Temperature lapse rate

This study examined 30-year of in situ observations (1981–2010) to determine monthly, and diurnal characteristics of near-surface temperature gradients (TG) in the Sudanese desert, both spatially and with elevation. The TG variation, along with its spatial and elevation dependence, forcing mechanisms for its variability, and its relationship with moisture and gradients of other climatic variables, were evaluated using a multi-collinearity approach and empirical analysis, respectively. A distinct annual cycle was observed in both the temperature gradient (or lapse rate) with elevation (TGE) and the temperature gradient with latitude (TGLat). The TGE is strongly negative during the warmer months (summer) and less strongly negative (or even positive) during the colder months (winter). However, for TGLat, the results are reversed. The mean TGE value steepens during the summer due to intense adiabatic cooling during the day and less inversion during the night, while this process is reversed for the observed shallower TGLat value in the same season. This result is attributed to desert characteristics at the northern lower elevations or higher latitudes, as well as the effects of the ITCZ, moisture, and cloud cover as a result of high elevations at lower latitudes in the south and southwest region. Low solar insolation, and Mediterranean cold airflow and littoral effect, combined with inversion and radiative cooling at lower elevations or northern higher latitudes, lead the TGE (TGLat) value to be shallow (steep) during the drier months. Excluding the inversion and radiative cooling at night, this effect is more pronounced in the winter. The extreme high and low values of TGE and TGLat, as well as their diurnal range, were found to strongly coincide with variations in the equatorial trough, as well as diurnal radiative energy differences and the regional synoptic phenomenon. In addition to being valuable for hydro-climatic, ecological, and agricultural modeling, this study can be replicated in other tropical desert areas around the world to gain a better understanding of desert’s climate.

A partir de dos campañas de medidas realizadas en verano en Carboneras (Almería) se establece el gradiente térmico vertical en la capa de aire superfi cial de una playa, al comparar las temperaturas de la arena y del aire. Del mismo modo, se miden las diferencias térmicas entre una pared encalada y una puerta oscura de una casa. Ambos casos revelan unas acusadas diferencias térmicas a escala microclimática, tanto en superfi cies naturales como artifi ciales, bajo radiación solar directa.

To accurately estimate near-surface (2 m) air temperatures in a mountainous region for hydrologic prediction models and other investigations of environmental processes, the authors evaluated daily and seasonal variations (with the consideration of different weather types) of surface air temperature lapse rates at a spatial scale of 10 000 km 2 in south-central Idaho. Near-surface air temperature data (T max , T min , and T avg) from 14 meteorological stations were used to compute daily lapse rates from January 1989 to December 2004 for a medium-elevation study area in south-central Idaho. Daily lapse rates were grouped by month, synoptic weather type, and a combination of both (seasonal-synoptic). Daily air temperature lapse rates show high variability at both daily and seasonal time scales. Daily T max lapse rates show a distinct seasonal trend, with steeper lapse rates (greater decrease in temperature with height) occurring in summer and shallower rates (lesser decrease in temperature with height) occurring in winter. Daily T min and T avg lapse rates are more variable and tend to be steepest in spring and shallowest in midsummer. Different synoptic weather types also influence lapse rates, although differences are tenuous. In general, warmer air masses tend to be associated with steeper lapse rates for maximum temperature, and drier air masses have shallower lapse rates for minimum temperature. The largest diurnal range is produced by dry tropical conditions (clear skies, high solar input). Cross-validation results indicate that the commonly used environmental lapse rate [typically assumed to be Ϫ0.65°C (100 m) Ϫ1 ] is solely applicable to maximum temperature and often grossly overestimates T min and T avg lapse rates. Regional lapse rates perform better than the environmental lapse rate for T min and T avg , although for some months rates can be predicted more accurately by using monthly lapse rates. Lapse rates computed for different months, synoptic types, and seasonal-synoptic categories all perform similarly. Therefore, the use of monthly lapse rates is recommended as a practical combination of effective performance and ease of implementation.

Land surface hydrological modeling is sensitive to near-surface air temperature, which is especially true for the cryosphere. The lapse rate of near-surface air temperature is a critical parameter when interpolating air temperature from station data to gridded cells. To obtain spatially distributed, fine-resolution near-surface (2 m) air temperature in the mainland China, monthly air temperature from 553 Chinese national meteorological stations (with continuous data from 1962 to 2011) are divided into 24 regional groups to analyze spatiotemporal variations of lapse rate in relation to surface air temperature and relative humidity. The results are as follows: (1) Evaluation of estimated lapse rate shows that the estimates are reasonable and useful for temperature-related analyses and modeling studies. (2) Lapse rates generally have a banded spatial distribution from southeast to northwest, with relatively large values on the Tibetan Plateau and in northeast China. The greatest spatial variability is in winter with a range of 0.3°C-0.9°C • 100 m À1 , accompanied by an inversion phenomenon in the northern Xinjiang Province. In addition, the lapse rates show a clear seasonal cycle. (3) The lapse rates maintain a consistently positive correlation with temperature in all seasons, and these correlations are more prevalent in the north and east. The lapse rates exhibit a negative relationship with relative humidity in all seasons, especially in the east. (4) Substantial regional differences in temporal lapse rate trends over the study period are identified. Increasing lapse rates are more pronounced in northern China, and decreasing trends are found in southwest China, which are more notable in winter. An overall increase of air temperature and regional variation of relative humidity together influenced the change of lapse rate.

The spatial distribution of surface air temperatures is essential for understanding and modelling high-relief environments. Good estimations of the surface temperature lapse rate (STLR) and the 0 C isotherm height (H0) are fundamental for hydrological modelling in mountainous basins. Although STLR changes in space and time, it is typically assumed to be constant leading to errors in the estimation of direct-runoff volumes and flash-floods risk assessment. This paper characterizes daily and seasonal temporal variations of the in-situ STLR and H0 over the western slope of the subtropical Andes (central Chile). We use temperature data collected during 2 years every 10 min by a 16 sensors network in a small catchment with elevations ranging between 700 and 3,250 m. The catchment drains directly into Santiago, the Chilean capital with more than seven million inhabitants. Resulting values are compared against those obtained using off-site, operational data sets. Significant intraand inter-day variations of the in-situ STLR were found, likely reflecting changes in the low-level temperature inversion during dry conditions. The annual average in-situ STLR is −5.9 C/km during wet-weather conditions. Furthermore, STLR and H0 estimations using off-site gauges are extremely sensitive to the existence of gauging stations at high elevations.

Land surface hydrological modeling is sensitive to near-surface air temperature, which is especially true for the cryosphere. The lapse rate of near-surface air temperature is a critical parameter when interpolating air temperature from station data to gridded cells. To obtain spatially distributed, fine-resolution near-surface (2 m) air temperature in the mainland China, monthly air temperature from 553 Chinese national meteorological stations (with continuous data from 1962 to 2011) are divided into 24 regional groups to analyze spatiotemporal variations of lapse rate in relation to surface air temperature and relative humidity. The results are as follows: (1) Evaluation of estimated lapse rate shows that the estimates are reasonable and useful for temperature-related analyses and modeling studies. (2) Lapse rates generally have a banded spatial distribution from southeast to northwest, with relatively large values on the Tibetan Plateau and in northeast China. The greatest spatial variability is in winter with a range of 0.3°C-0.9°C • 100 m À1 , accompanied by an inversion phenomenon in the northern Xinjiang Province. In addition, the lapse rates show a clear seasonal cycle. (3) The lapse rates maintain a consistently positive correlation with temperature in all seasons, and these correlations are more prevalent in the north and east. The lapse rates exhibit a negative relationship with relative humidity in all seasons, especially in the east. (4) Substantial regional differences in temporal lapse rate trends over the study period are identified. Increasing lapse rates are more pronounced in northern China, and decreasing trends are found in southwest China, which are more notable in winter. An overall increase of air temperature and regional variation of relative humidity together influenced the change of lapse rate.

Snowpack is an important source of freshwater. Snowmelt runoff models provide a means to predict the timing and magnitude of spring snowmelt. This study assessed the sensitivity of the conceptual, degreeday Snowmelt Runoff Model (SRM) to snow covered area and temperature inputs in a small mountainous catchment in Utah, USA. It was found that snow cover products from the Moderate Resolution Imaging Spectroradiometer (MODIS) underestimate snow covered area during the second half of the melt season, leading to inadequate modeling of spring snowmelt with SRM (Nash-Sutcliffe Efficiency ¼ 0.59; bias of À26.9%). Incorporation of ancillary snow covered area information provided by Landsat ETMþ imagery greatly improved streamflow simulations (Nash-Sutcliffe Efficiency ¼ 0.92; bias of À0.01%). For the temperature input, SRM appeared more sensitive to the elevation and location of the temperature reference station than to the lapse rate scenario used to extrapolate temperatures throughout the watershed. These findings will be useful for snowmelt runoff research and water resource management.

h i g h l i g h t s Both long-term and short-term study reveals an increase in pollutant concentration. PM10 has been found to be the most dominant air pollutants during this Deepawali. Boundary layer is affected by retained change in lapse rate and low relative humidity. Windrose diagram also validated the cause of severe urban Deepawali pollution. Increased pollution is a serious concern on the changing pattern of environment.

This study presents the first results of monthly, seasonal and annual characteristics of temperature lapse rate on the southern slope of the central Himalayas, based on 20 years record of surface air temperature at 56 stations in Nepal. These stations are located at a range of elevations between 72 and 3,920 m above sea level. It is proven that the lapse rate can be calculated with a linear regression model. The annual cycle of temperature lapse rate exhibits a bi-modal pattern: two maxima in the pre-and postmonsoon seasons respectively separated by two minima in winter and summer, respectively. This pattern is different from the findings from the other mountain regions and suggests different controlling factors in the individual seasons. The highest temperature lapse rate occurs in the premonsoon and is associated with strong dry convection (i.e., corresponding to the clear weather season and considerable sensible heat flux). The post-monsoon has the second highest lapse rate, and its cause is similar to the pre-monsoon season but with a relatively small thermal forcing effect after the rainy summer. The lowest lapse rate occurs in winter and is associated with strong radiative cooling and cold air flows over low-elevation areas. The summer lapse rate minimum is due to latent heating over the higher elevations and reduced solar heating over the lower elevations.

This study examined 30-year of in situ observations (1981–2010) to determine monthly,
and diurnal characteristics of near-surface temperature gradients (TG) in the Sudanese
desert, both spatially and with elevation. The TG variation, along with its spatial and
elevation dependence, forcing mechanisms for its variability, and its relationship with
moisture and gradients of other climatic variables, were evaluated using a multi-collinearity
approach and empirical analysis, respectively. A distinct annual cycle was observed in both
the temperature gradient (or lapse rate) with elevation (TGE) and the temperature gradient
with latitude (TGLat). The TGE is strongly negative during the warmer months (summer) and
less strongly negative (or even positive) during the colder months (winter). However, for
TGLat, the results are reversed. The mean TGE value steepens during the summer due to
intense adiabatic cooling during the day and less inversion during the night, while this
process is reversed for the observed shallower TGLat value in the same season. This result
is attributed to desert characteristics at the northern lower elevations or higher latitudes, as
well as the effects of the ITCZ, moisture, and cloud cover as a result of high elevations at
lower latitudes in the south and southwest region. Low solar insolation, and Mediterranean
cold airflow and littoral effect, combined with inversion and radiative cooling at lower
elevations or northern higher latitudes, lead the TGE (TGLat) value to be shallow (steep)
during the drier months. Excluding the inversion and radiative cooling at night, this effect is
more pronounced in the winter. The extreme high and low values of TGE and TGLat, as well
as their diurnal range, were found to strongly coincide with variations in the equatorial
trough, as well as diurnal radiative energy differences and the regional synoptic
phenomenon. In addition to being valuable for hydro-climatic, ecological, and
agricultural modeling, this study can be replicated in other tropical desert areas around
the world to gain a better understanding of desert’s climate.

It is generally accepted that the observed warming of our climate system is amplified in the Arctic. In contrast, despite model predictions of future amplified warming in high elevation regions, analyses of limited mountain observations available do not always agree. This is partly because of inherent complexities in mountain climate, but also because current monitoring is inadequate and skewed towards lower elevations. We review important physical mechanisms which could potentially contribute to elevation-dependent warming (EDW) that include: a) snow albedo and surface-based feedbacks, b) water vapour changes and latent heat release, c) surface water vapour and radiative flux changes, d) surface heat loss and temperature change, and e) aerosols. Mechanisms either encourage an enhancement of warming with elevation, or enhance warming in a critical elevation band. The variable combination of mechanisms may cause contrasting patterns of EDW in different regions. We propose future needs to improve knowledge of mountain temperature trends and their controlling mechanisms through improved observations, use of satellite data, and model simulations. Improved understanding of EDW is of critical societal importance because EDW can enhance climate change impacts in mountain ecosystems by accelerating changes in cryospheric systems, hydrological regimes, ecosystem response and biodiversity.

INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. 27: 385–398 (2007) Published online 28 September 2006 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/joc.1396 ... Near-surface-temperature lapse rates on the Prince of Wales

Land surface temperature (LST) is an important parameter in the study of the physical processes of land surface. Understanding the surface temperature lapse rate (TLR) can help to reveal the characteristics of mountainous climates and regional climate change. A methodology was developed to calculate and analyze land-surface TLR in China based on grid datasets of MODIS LST and digital elevation model (DEM), with a formula derived on the basis of the analysis of the temperature field and the height field, an image enhancement technique used to calculate gradient, and the fuzzy c-means (FCM) clustering applied to identify the seasonal pattern of the TLR. The results of the analysis through the methodology showed that surface temperature vertical gradient inversion widely occurred in Northeast, Northwest, and North China in winter, especially in the Xinjiang Autonomous Region, the northern and the western parts of the Greater Khingan Mountains, the Lesser Khingan Mountains, and the nort...

Based on monthly mean, maximum, and minimum air temperature and monthly mean precipitation data from 10 meteorological stations on the southern slope of the Mt. Qomolangma region in Nepal between 1971 and 2009, the spatial and temporal characteristics of climatic change in this region were analyzed using climatic linear trend, Sen's Slope Estimates and Mann-Kendall Test analysis methods. This paper focuses only on the southern slope and attempts to compare the results with those from the northern slope to clarify the characteristics and trends of climatic change in the Mt. Qomolangma region. The results showed that: (1) between 1971 and 2009, the annual mean temperature in the study area was 20.0℃, the rising rate of annual mean temperature was 0.25℃/10a, and the temperature increases were highly influenced by the maximum temperature in this region. On the other hand, the temperature increases on the northern slope of Mt. Qomolangma region were highly influenced by the minimum temperature. In 1974 and 1992, the temperature rose noticeably in February and September in the southern region when the increment passed 0.9℃. (2) Precipitation had an asymmetric distribution; between 1971 and 2009, the annual precipitation was 1729.01 mm. In this region, precipitation showed an increasing trend of 4.27 mm/a, but this was not statistically significant. In addition, the increase in rainfall was mainly concentrated in the period from April to October, including the entire monsoon period (from June to September) when precipitation accounts for about 78.9% of the annual total. (3) The influence of altitude on climate warming was not clear in the southern region, whereas the trend of climate warming was obvious on the northern slope of Mt. Qomolangma. The annual mean precipitation in the southern region was much higher than that of the northern slope of the Mt. Qomolangma region. This shows the barrier effect of the Himalayas as a whole and Mt. Qomolangma in particular.

The 2007 European larch (Larix decidua Mill.) growing season was monitored along two elevational transects in the Lötschental valley in the Swiss Alps. Phenological observations and weekly microcore sampling of 28 larch trees were conducted between April and October 2007 at seven study sites regularly spaced from 1350 to 2150 m a.s.l. on northwest-and southeast-facing slopes. The developmental stages of nearly 75,000 individual cells assessed on 1200 thin sections were used to investigate the links between the trees' thermal regimes and growth phases including the beginning and ending of cell enlargement, wall thickening and maturation of the stem wood. Needles appeared~3-4 weeks earlier than stem growth. The duration of ring formation lasted from mid-May to the end of October, with the length of the growing season decreasing along elevation from 137 to 101days. The onset of the different growing seasons changed by 3-4 days per 100 m elevation; the ending of the growing season, however, appeared minimally related to altitude. If associated with the monitored altitudinal lapse rate of −0.5°C per 100 m, these results translate into a lengthening of the growing season bỹ 7 days per degree Celsius. This study provides new data on the timing and duration of basic growth processes and contributes to quantification of the impacts of global warming on tree growth and productivity.

A high elevation data set of surface temperatures from the Front Range of the Rocky Mountains in Colorado, USA, is analysed for evidence of long-term change (1952-98). Sites range from the high plains of Colorado (1509 m) to the alpine tundra (3749 m). Systematic changes in surface-based lapse rates are uncovered, with absolute cooling at the highest elevations, but little temperature change on the high plains. There is lapse-rate steepening at the higher elevations (>3000 m). A synoptic analysis using gridded pressure data shows lapse rate changes to be largely independent of synoptic type. Radiosonde ascents from Denver (1956-98) and Grand Junction (1946-98) are used to derive air equivalent temperatures (AETs) at the same elevations as the surface records. AETs show a contrasting temporal trend, with absolute warming at all levels. Furthermore, free-air lapse rates are weakening at higher elevations, the warming becoming stronger with height. A comparison of the two data sets through derivation of free-air-surface temperature differences shows that the alpine tundra zone of the high Rockies is becoming a progressively stronger heat sink. Possible explanations include increased snow cover, enhanced air movement over the surface and decreased solar radiation input. The heat sink enhancement has led to rapid cooling in the alpine tundra that could not be predicted from the free-air record, casting doubt upon the strong dependence on free-air temperature changes in climate modelling when investigating the potential effects of global warming in mountainous regions. In addition, these local surface trends are of the opposite sign to global and other regional trends identified in many recent observational and modelling studies.

The study of spatiotemporal variation in temperature is vital to assess changes in climate, especially in the Himalayan region, where the livelihoods of billions of people living downstream depend on water coming from the melting of snow and glacier ice. To this end, temperature trend analysis is carried out in the Narayani River basin, a major river basin of Nepal, characterized by three climatic regions: tropical, subtropical and alpine. Temperature data from six stations located within the basin were analyzed. The elevation of these stations ranges from 460 to 3800 m a.s.l. and the time period of available temperature data ranges from 1960–2015. Multiple regression and empirical mode decomposition (EMD) methods were applied to fill in missing data and to detect trends. Annual as well as seasonal trends were analyzed and a Mann–Kendall test was employed to test the statistical significance of detected trends. The results indicate significant cooling trends before the 1970s, and warming trends after the 1970s in the majority of the stations. The warming trends range from 0.028 to 0.035 ∘C year−1 with a mean increasing trend of 0.03 ∘C year−1 after 1971. Seasonal trends show the highest warming trends in the monsoon season, followed by winter and the premonsoon and postmonsoon season. However, the difference in warming rates between different seasons was not significant. An average temperature lapse rate of −0.006 ∘C m−1 with the steepest value (−0.0064 ∘C m−1) in the pre-monsoon season and the least negative (−0.0052 ∘C m−1) in the winter season was observed for this basin. A comparative analysis of the gap-filled data with freely available global climate dataset show reasonable correlation, thus confirming the suitability of the gap-filling methods

The South Asian summer monsoon brings abundant precipitation and associated latent heat release to the south of central Himalaya, and alters hydrothermal conditions of this region. This study explored the impact of South Asian summer monsoon on the elevation-dependence of meteorological variables along the south slope of Mt. Everest in the central Himalaya, which is crucial to modelling the glacio-hydrological processes in this elevated region. The data were collected at five stations deployed at 2660-5600 m above sea level (asl) along the slope during 2007-2011. Major findings are the following: (1) The amount of precipitation during the monsoon season usually decreases with elevation but it is relatively uniform between 3600 and 5000 m asl. This uniform profile may be attributed to the monsoon-terrain-land interactions, particularly to the retard effect of glacier cooling on daytime upvalley wind; (2) Cloud shielding effects cause lower solar radiation and higher downward longwave radiation in the monsoon than in the other seasons. In particular, higher elevations have more clouds in the afternoon, resulting in an abnormal elevation-dependence of solar radiation (i.e. higher elevations receive less solar radiation); (3) Strong daytime upvalley wind and moist convection homogenizes the vertical distributions of air mass along the slope, causing a constant lapse rate of both surface air temperature and dew-point temperature (representing humidity) during typical monsoon months, but this phenomenon is not found in the other seasons. These findings provide critical guidance for extrapolating the meteorological variables from lower to higher elevations in this region.

To accurately estimate near-surface (2 m) air temperatures in a mountainous region for hydrologic prediction models and other investigations of environmental processes, the authors evaluated daily and seasonal variations (with the consideration of different weather types) of surface air temperature lapse rates at a spatial scale of 10 000 km 2 in south-central Idaho. Near-surface air temperature data (T max , T min , and T avg ) from 14 meteorological stations were used to compute daily lapse rates from January 1989 to December 2004 for a medium-elevation study area in south-central Idaho. Daily lapse rates were grouped by month, synoptic weather type, and a combination of both (seasonal-synoptic). Daily air temperature lapse rates show high variability at both daily and seasonal time scales. Daily T max lapse rates show a distinct seasonal trend, with steeper lapse rates (greater decrease in temperature with height) occurring in summer and shallower rates (lesser decrease in temperature with height) occurring in winter. Daily T min and T avg lapse rates are more variable and tend to be steepest in spring and shallowest in midsummer. Different synoptic weather types also influence lapse rates, although differences are tenuous. In general, warmer air masses tend to be associated with steeper lapse rates for maximum temperature, and drier air masses have shallower lapse rates for minimum temperature. The largest diurnal range is produced by dry tropical conditions (clear skies, high solar input). Cross-validation results indicate that the commonly used environmental lapse rate [typically assumed to be Ϫ0.65°C (100 m) Ϫ1 ] is solely applicable to maximum temperature and often grossly overestimates T min and T avg lapse rates. Regional lapse rates perform better than the environmental lapse rate for T min and T avg , although for some months rates can be predicted more accurately by using monthly lapse rates. Lapse rates computed for different months, synoptic types, and seasonal-synoptic categories all perform similarly. Therefore, the use of monthly lapse rates is recommended as a practical combination of effective performance and ease of implementation.

Studies on climate change in the last two decades are growing rapidly that might have shadowed some of the other fields of studies. The changes have spatial characteristics and studies are yet to cover many isolated areas of the world. Existing literature showed abrupt change in the Himalaya climate. However, such generalisations are not appropriate for the Himalaya because of the complex topography of the region that has caused several microclimates in the region. Understanding climate dynamism in microclimatic regions is an important component of climate change research, particularly to comprehend impacts of climate change on the social-ecological systems of the Himalaya and to assess adaptive capacity of the communities. This paper examines climate dynamics in the Himalaya in reference to the meteorological records of four decades (1971-2010) at three stations of the Kaligandaki Basin. The findings suggest that the climates of the basin are changed, with variable rates across the stations located at different ecological zones. The extreme maximum and maximum temperatures of Lumle and Rampur stations, minimum temperature of Jomsom and Rampur stations, and extreme minimum temperatures of all of the studied meteorological stations increased significantly. Contrary to the increase in the temperatures, precipitation data revealed trend-less but inter-annual variability. Annual numbers of wet-days weredecreased at Rampur and Lumle stations while rainy days were increased at Jomsom. In addition, extreme rainfall events were increased in general in the basin.

Screen temperatures were monitored from May 2001 to April 2003 in an array of 25 sites on the Prince of Wales Icefield, Ellesmere Island, Canada. The observational network covered an area of ca 15 650 km 2 and spanned an altitude ranging from 130 to 2010 m above sea level. The spatial array provides a record of near-surface-temperature lapse rates and mesoscale temperature variability on the icefield. The mean daily lapse rate in the 2-year record is −4.1°C km −1 , with an average summer lapse rate of −4.3°C km −1 . Surface-temperature lapse rates in the region are therefore systematically less than the free-air lapse rates that are typically adopted for extrapolations of sea-level temperature to higher altitudes. Steep lapse rates, resembling moist adiabatic rates in the free air (−6 to −7°C km −1 ), are more common in summer at our site and are associated with enhanced cyclonic activity (low-pressure and high relative vorticity) and southerly flow aloft. In contrast, northerly, anticyclonic flow prevails when summer lapse rates are weak (above −2°C km −1 ). The low surface-temperature lapse rates and their systematic synoptic variability have important implications for applications that require downscaling or extrapolation of surface-or boundary-layer temperatures, such as modelling of glacier mass balance. We illustrate this in an analysis of observed versus modelled snowmelt on the icefield. . This choice is based on average observed lapse rates in the free atmosphere, and represents a typical moist adiabatic cooling rate .

Temperature trend magnitudes at 71 homogenized surface stations with elevations above 2000 m asl in the eastern and central Tibetan Plateau (TP) and 56 grid points from surface NCEP and ERA-40 reanalyses in the TP's vicinity are examined. Both the surface meteorological stations and ERA-40 show general warming trends at the majority of locations, especially in winter. NCEP fails to identify this. Compared with the surface stations, both NCEP and ERA-40 reanalysis data underestimate air temperature trends in the TP, but ERA-40 is better than NCEP. There are no simple linear relationships between elevation and temperature trend magnitudes on an annual or seasonal basis in the surface data or ERA-40, and in NCEP this relationship is inconsistent. Instead there are significant correlations between mean annual and seasonal temperatures and temperature trend magnitudes in the surface dataset and NCEP data (but not ERA-40). We suggest this is due to cryospheric feedback since trends are enhanced when mean annual temperatures are near freezing. The absence of any simple elevation dependency in temperature trends suggests that the rapid warming rate derived from high elevation ice-cores in this region should be interpreted with caution. In addition, more attention should be given to the selection of reanalysis to represent surface climate in the TP, since topographical differences between grid points and stations, and other reanalysis model differences such as surface land schemes, cause differences in trend identification and patterns in this critical region.

Estimates of the tropospheric lapse rate γ and analysis of its relation to the surface temperature T s in the annual cycle and interannual variability have been made using the global monthly mean data of the NCEP/NCAR reanalysis . The tropospheric lapse rate γ is about 6.1 K/km in the Northern Hemisphere (NH) as a whole and over the ocean and about 6.2 K/km over the continents. The value of γ decreases from 6.5 K/km at low latitudes to 4.5 K/km at polar latitudes. The values of d γ / dT s , the parameter of sensitivity of γ to the variation of T s for the NH in the interannual variability, are found to be about 0.04 km -1 (0.041 km -1 for the NH as a whole, 0.042 km -1 over the ocean, and 0.038 km -1 over the continents). This corresponds to an increase in γ of approximately 0.7% when the surface temperature of the NH is increased by 1 K. Estimates of d γ / dT s vary from about 0.05 km -1 in the subtropics to 0.10 km -1 at polar latitudes. When d γ / dT s is positive, the surface and tropospheric warming means a temperature decrease above a certain critical level H cr . The height of the level H cr with constant temperature, which is defined by the inverse value ( d γ / dT s ) -1 , is about 25 km for the NH as a whole, i.e., above the tropopause. In the subtropics, H cr is about 20 km. At polar latitudes, H cr decreases to about 10 km. Positive values of d γ / dT s characterize a positive climatic feedback through the lapse rate and indicate a general decrease in the static stability of the troposphere during global warming. Along with a general tendency of γ to increase with rising T s , there are regional regimes with the opposite tendency, mainly over the ocean. The negative correlation of γ with T s is found over the oceanic tropics and midlatitudes, in particular, over the oceanic belt around Antarctica.

A high elevation data set of surface temperatures from the Front Range of the Rocky Mountains in Colorado, USA, is analysed for evidence of long-term change . Sites range from the high plains of Colorado (1509 m) to the alpine tundra (3749 m). Systematic changes in surface-based lapse rates are uncovered, with absolute cooling at the highest elevations, but little temperature change on the high plains. There is lapse-rate steepening at the higher elevations (>3000 m). A synoptic analysis using gridded pressure data shows lapse rate changes to be largely independent of synoptic type. Radiosonde ascents from Denver (1956-98) and Grand Junction (1946-98) are used to derive air equivalent temperatures (AETs) at the same elevations as the surface records. AETs show a contrasting temporal trend, with absolute warming at all levels. Furthermore, free-air lapse rates are weakening at higher elevations, the warming becoming stronger with height. A comparison of the two data sets through derivation of free-air-surface temperature differences shows that the alpine tundra zone of the high Rockies is becoming a progressively stronger heat sink. Possible explanations include increased snow cover, enhanced air movement over the surface and decreased solar radiation input. The heat sink enhancement has led to rapid cooling in the alpine tundra that could not be predicted from the free-air record, casting doubt upon the strong dependence on free-air temperature changes in climate modelling when investigating the potential effects of global warming in mountainous regions. In addition, these local surface trends are of the opposite sign to global and other regional trends identified in many recent observational and modelling studies. N. PEPIN AND M. LOSLEBEN rates at high elevations. Alternative theories have thus been expounded to explain decreased sensitivity to climate change at high elevations . Analyses in the tropics have identified elevation dependency in the free air with radiosonde data showing a rapid rise in tropical freezing heights and increased warming with height . This is associated with an enhanced hydrological cycle and decreased free-air lapse rates in a moister atmosphere. The enhanced melting of tropical glaciers on Mount Kenya and Kilimanjaro (Hastenrath and Greischar, 1997; is taken as further evidence of enhanced warming at high surface elevations in the tropics, although long series of high-elevation temperature data are unavailable.

Temperature trend magnitudes at 71 homogenized surface stations with elevations above 2000 m asl in the eastern and central Tibetan Plateau (TP) and 56 grid points from surface NCEP and ERA-40 reanalyses in the TP's vicinity are examined. Both the surface meteorological stations and ERA-40 show general warming trends at the majority of locations, especially in winter. NCEP fails to identify this. Compared with the surface stations, both NCEP and ERA-40 reanalysis data underestimate air temperature trends in the TP, but ERA-40 is better than NCEP. There are no simple linear relationships between elevation and temperature trend magnitudes on an annual or seasonal basis in the surface data or ERA-40, and in NCEP this relationship is inconsistent. Instead there are significant correlations between mean annual and seasonal temperatures and temperature trend magnitudes in the surface dataset and NCEP data (but not ERA-40). We suggest this is due to cryospheric feedback since trends are enhanced when mean annual temperatures are near freezing. The absence of any simple elevation dependency in temperature trends suggests that the rapid warming rate derived from high elevation ice-cores in this region should be interpreted with caution. In addition, more attention should be given to the selection of reanalysis to represent surface climate in the TP, since topographical differences between grid points and stations, and other reanalysis model differences such as surface land schemes, cause differences in trend identification and patterns in this critical region.

1] Most climate models suggest amplification of global warming in high mountains, but observations are less clear. Using comprehensive, homogeneity-adjusted temperature records from over 1000 high elevation stations across the globe, we examine the causes of changing temperature trends with elevation, assessing the roles of free atmospheric change, topography (exposure and aspect), and cryospheric feedback. The data show that observed 20th century temperature trends are most rapid near the annual 0°C isotherm due to snow-ice feedback. Mountain summit and freely draining slope sites are dominated by free-air advection and thus have consistent trend magnitudes, with reduced inter-site variance in comparison with incised valley sites where local factors are more important. Thus, while there has been no simplistic elevational increase in warming rates, some generalizations can be made. Water resources and ecosystems near the 0°C isotherm in the extratropics are at increased risk from accelerated warming. The data also suggest that exposed mountain summits, away from the effects of urbanization and topographic sheltering, may provide a relatively unbiased record of the planet's climate.

To develop a finescale dataset for the purpose of analyzing historical climatic change over the Tibet Plateau
(TP), a high-resolution regional climate simulation for 1979–2011 was conducted using the Weather Research
and Forecasting (WRF)Model driven by the ERA-Interim(ERA-Int). This work evaluates the high-resolution
(30 km) WRF simulation in terms of annual variation, spatial structure, and 33-yr temporal trends of surface
air temperature (Tair) and precipitation (Prec) over the TP, with reference to station observations. Another
focus is on the examination of the height–temperature relationship. Inheriting from its forcing, the WRF
simulation presents an apparent cold bias in the TP. The cold bias is largely reduced by a lapse rate correction
of the simulated surface air temperature with help of the station and model elevations. ERA-Int presents the
same sign of Tair and Prec trends as the observations, but with smaller magnitude, especially in the dry season.
Compared to its forcing, the WRF simulation improves the simulation of the annual cycles and temporal
trends of Tair and Prec in the wet season. In the dry season, however, there is hardly any improvement. The
observed Tair presents a downward linear trend in the lapse rate. This feature is examined in the WRF
simulation in comparison to ERA-Int. TheWRFsimulation captures the observed lapse rate and its temporal
trend better than ERA-Int. The decreasing lapse rate over time confirms that Tair change in the TP is
elevation dependent.

Land surface hydrological modeling is sensitive to near-surface air temperature, which is especially true for the cryosphere. The lapse rate of near-surface air temperature is a critical parameter when interpolating air temperature from station data to gridded cells. To obtain spatially distributed, fine-resolution near-surface (2 m) air temperature in the mainland China, monthly air temperature from 553 Chinese national meteorological stations (with continuous data from 1962 to 2011) are divided into 24 regional groups to analyze spatiotemporal variations of lapse rate in relation to surface air temperature and
relative humidity. The results are as follows: (1) Evaluation of estimated lapse rate shows that the estimates are reasonable and useful for temperature-related analyses and modeling studies. (2) Lapse rates generally have a banded spatial distribution from southeast to northwest, with relatively large values on the Tibetan Plateau and in northeast China. The greatest spatial variability is in winter with a range of 0.3°C–0.9°C · 100m
1, accompanied
by an inversion phenomenon in the northern Xinjiang Province. In addition, the lapse rates show a clear seasonal cycle. (3) The lapse rates maintain a consistently positive correlation
with temperature in all seasons, and these correlations are more prevalent in the north and
east. The lapse rates exhibit a negative relationship with relative humidity in all seasons,
especially in the east. (4) Substantial regional differences in temporal lapse rate trends over the study period are identified. Increasing lapse rates are more pronounced in northern China, and decreasing trends are found in southwest China, which are more notable in
winter. An overall increase of air temperature and regional variation of relative humidity together influenced the change of lapse rate.

High topographies, such as the Tibetan plateau (TP) in China, have been considered as the sensitive areas in response to global climate change. By analyzing the relationship between warming structure and altitude (1 000-5 000 m) in the TP and its vicinities using the 46-year January mean observed temperature data, we found that there was a significant altitude effect of temperature warming onset time (mutation time) on the plateau and the neighboring regions: the higher the altitude, the later the climate warming happens, and vice versa. There also seems a slight altitude effect on warming magnitude: the higher the altitude, the less the warming magnitude. Therefore, the temperature warming in the high altitude area of the TP (below 5 000 m) responds to global warming less sensitively than the low-altitude neighboring areas both in onset time and magnitude, which may be mainly caused by high albedo and large thermal capacity of the ice/snow cover on the higher part of the plateau and possible heat island effect in the lower part of the plateau. KEY WORDS: climatic variation, Tibetan plateau, altitude effect.

Temperature trend magnitudes at 71 homogenized surface stations with elevations above 2000 m asl in the eastern and central Tibetan Plateau (TP) and 56 grid points from surface NCEP and ERA-40 reanalyses in the TP's vicinity are examined. Both the surface meteorological stations and ERA-40 show general warming trends at the majority of locations, especially in winter. NCEP fails to identify this. Compared with the surface stations, both NCEP and ERA-40 reanalysis data underestimate air temperature trends in the TP, but ERA-40 is better than NCEP. There are no simple linear relationships between elevation and temperature trend magnitudes on an annual or seasonal basis in the surface data or ERA-40, and in NCEP this relationship is inconsistent. Instead there are significant correlations between mean annual and seasonal temperatures and temperature trend magnitudes in the surface dataset and NCEP data (but not ERA-40). We suggest this is due to cryospheric feedback since trends are enhanced when mean annual temperatures are near freezing. The absence of any simple elevation dependency in temperature trends suggests that the rapid warming rate derived from high elevation ice-cores in this region should be interpreted with caution. In addition, more attention should be given to the selection of reanalysis to represent surface climate in the TP, since topographical differences between grid points and stations, and other reanalysis model differences such as surface land schemes, cause differences in trend identification and patterns in this critical region.

1] Land surface hydrological modeling is sensitive to near-surface air temperature, which is especially true for the cryosphere. The lapse rate of near-surface air temperature is a critical parameter when interpolating air temperature from station data to gridded cells. To obtain spatially distributed, fine-resolution near-surface (2 m) air temperature in the mainland China, monthly air temperature from 553 Chinese national meteorological stations (with continuous data from 1962 to 2011) are divided into 24 regional groups to analyze spatiotemporal variations of lapse rate in relation to surface air temperature and relative humidity. The results are as follows: Evaluation of estimated lapse rate shows that the estimates are reasonable and useful for temperature-related analyses and modeling studies.

This study presents the first results of monthly, seasonal and annual characteristics of temperature lapse rate on the southern slope of the central Himalayas, based on 20 years record of surface air temperature at 56 stations in Nepal. These stations are located at a range of elevations between 72 and 3,920 m above sea level. It is proven that the lapse rate can be calculated with a linear regression model. The annual cycle of temperature lapse rate exhibits a bi-modal pattern: two maxima in the pre-and postmonsoon seasons respectively separated by two minima in winter and summer, respectively. This pattern is different from the findings from the other mountain regions and suggests different controlling factors in the individual seasons. The highest temperature lapse rate occurs in the premonsoon and is associated with strong dry convection (i.e., corresponding to the clear weather season and considerable sensible heat flux). The post-monsoon has the second highest lapse rate, and its cause is similar to the pre-monsoon season but with a relatively small thermal forcing effect after the rainy summer. The lowest lapse rate occurs in winter and is associated with strong radiative cooling and cold air flows over low-elevation areas. The summer lapse rate minimum is due to latent heating over the higher elevations and reduced solar heating over the lower elevations.