Papers by Kevin Trenberth
Heat budgets and poleward atmospheric energy transports [presentation]
Reply to Rajagopalan, Lall and Cane's comment about "The interpretation of short climate records with comments on the North Atlantic and Southern Oscillations
Bulletin of the American Meteorological Society, 1999
Are Recent Hurricane (Harvey, Irma, Maria) Disasters Natural?
98th American Meteorological Society Annual Meeting, Jan 9, 2018
Earth’s changing energy budget
AGU Fall Meeting Abstracts, Dec 9, 2019
Was there a hiatus in the rise of global mean surface temperatures and is it over
AGU Fall Meeting Abstracts, Dec 17, 2015
An evaluation is carried out of the moisture fields, the precipitation P and evaporation E, and t... more An evaluation is carried out of the moisture fields, the precipitation P and evaporation E, and the moisture transport and divergence in the atmosphere from the global atmospheric National Centers for Environmental Prediction (NCEP) reanalyses produced with fourdimensional-data assimilation. The moisture fields are summarized by the precipitable water which is compared with analyzed fields from NVAP based primarily on Special Sensor Microwave Imager (SSM/I) over the oceans and rawinsonde measurements over land, plus TIROS Operational Vertical Sounder (TOVS). The moisture budgets are evaluated through computation of the freshwater flux at the surface E -P using residual techniques from the divergence of the total moisture transport, and this is compared with the reanalysis E -P that is based upon a 6-hour integration of the assimilating model and thus depends on the model parameterizations. The P field is evaluated using Xie-Arkin Global Precipitation Climatology Project (GPCP) estimates. An atlas presents climatological means for the period 1979 to 1995 (17 years) and standard deviations for annual; seasonal and monthly values, and the differences between estimates. Anomalies for all the seasons throughout this period are presented for many fields. All of the fields are available online. The NCEP moisture fields are shown to contain large and significant negative biases in the tropics. Moisture is deficient in the tropical convergence zones by 4 to 12 mm (out of 40 to 50 mm), and values are too high in the South Pacific High. The tropical structures are less well defined in the NCEP reanalyses and values are generally smaller where they should be high and higher where they should be low. In addition, the NCEP fields reveal much less variability from year to year in analysed precipitable water in the tropical Pacific than in the NVAP data, and moreover, the correlation shows that the variations that are present along the ITCZ are not very well related to those in the real world. Dominant variations are found in the tropical Pacific in association with the El Ninio-Southern Oscillation (ENSO) phenomenon, but the NCEP fields are especially deficient in the central and western tropical Pacific in all seasons. Although the GPCP product contains considerable uncertainties, the patterns are believed to be reliable and good enough to show that there are substantial biases in the NCEP P. The NCEP model P generally reveals a pronounced double intertropical convergence zone (ITCZ) in the central Pacific and the location of the South Pacific Convergence Zone (SPCZ) is not well captured. Rainfall amounts are much lower than observed in the tropical convergence zones. The standard deviation maps reveal that the variability in the V central tropical Pacific of P associated with ENSO is severely underestimated in the NCEP reanalyses, and moreover, is not very well correlated with the GPCP product. A bias for too much rainfall in the model over the southeastern U.S. is also present in northern summer. In places where P is strong, especially the ITCZs, there is a low bias in model P, probably associated with the low bias in moisture. Thus the deficit in precipitable water could be a factor in contributing to lower rainfall rates in the tropics and, at the same time, lower rainfalls mean lower latent heating and feedback to the divergent flow which transports the moisture into the region, thereby contributing to biases in moisture amounts. It is likely that a good portion of the biases in P are also reflected in E -P, the fresh water surface flux. The comparison of E -P from the moisture budget with the model result reveals similarities, apparently reflecting the common influence of the circulation divergence, however, there are also strong and systematic differences. In particular, remarkably, nearly all island stations show up as bull's-eyes in the difference field. These are identified as originating from the moisture budget calculation through rather subtle effects arising from small but systematic differences in vertical moisture profiles from those in the surrounding oceans. In part this may reflect differences between radiosonde moisture amounts with either the model first guess or TOVS soundings. It does indicate that the influence radius of rawinsonde moisture observations, while perhaps appropriate for an individual sounding, is probably too small in the analyses of these data on average. It is difficult to comment on the other fields as there is no direct means of validation. On an annual mean basis the largest evaporation of over 6 mm/day is in the subtropical Indian Ocean, as was also found in ECMWF analyses. There seem to be places where biases in E are present, as seen in E -P differences, and they are probably associated with spurious land moisture sources in some cases. Although the fields analysed here are interesting, their substantial shortcomings mean that they should only be used with great caution in climate and hydrological studies. A discussion is given of sources of errors contributing to the moisture budgets. Cover: The cover figure depicts the annual average total vertically integrated moisture transport, as vectors, from the NCEP reanalyses in kg (m s) -1 . The 150 unit contour of the magnitude is shown. Acknowledgments: This research is partly sponsored by NOAA under grant NA56GP0247 and by NASA under NASA Order No. W-18,077. Thanks to Doug Lindholm who prepared all the data sets for our use and Phil Arkin and Pingping Xie for the rainfall dataset. vi __ Annual 1979-95 mean (mm day ' 1 ) Precipitable water (NCEP) March 1979-95 mean Precipitable water (NCEP) March 1979-95 Std. Dev. 90N I ...
Current climate change reports, Aug 16, 2015
Recently available model ensembles have created an unprecedented opportunity for exploring and na... more Recently available model ensembles have created an unprecedented opportunity for exploring and narrowing uncertainty in one of climate's benchmark indices, equilibrium climate sensitivity. A range of novel approaches for constraining the raw sensitivity estimates from these ensembles with observations has also been proposed, applied, and explored in a diversity of contexts. Through subsequent analysis, an increased understanding of the relative merits and limitations of these methods has been gained and their refinement and optimal implementation continue to be actively studied and debated with the hopes of reducing uncertainty in one of climate science's most persistent and elusive measures.
Climate research [2]
Issues in Science and Technology, Mar 1, 2003
Challenges of the surface energy budget and proposed ways forward
EGU General Assembly Conference Abstracts, Apr 1, 2015
In 50 years, will global warming have had any positive effects on Americans?
The crisis in New Zealand meteorology
Search, 1992
Diagnostics of vertically integrated fluxes of energy [presentation]
Global energy and moisture budgets of the atmosphere [presentation]
University Science Books, 2000
The cover photograph of the effects of drought on a farm in eastern Colorado in 1977 is prototypi... more The cover photograph of the effects of drought on a farm in eastern Colorado in 1977 is prototypical of scenes in the 1930s during the "dust bowl" era. The risk of such droughts with global warming increases owing to increased drying of the landscape.
Climate Dynamics, Mar 19, 2016
OHC variability are too weak and the tropical zonal mean ENSO signal is strongly underestimated o... more OHC variability are too weak and the tropical zonal mean ENSO signal is strongly underestimated or even completely missing in most of the considered models. Results suggest that attempts to infer insight about climate sensitivity from ENSO-related variability are likely to be hampered by biases in ENSO in CMIP simulations that do not bear a clear link to future changes. Electronic supplementary material The online version of this article (doi:10.1007/s00382-016-3057-z) contains supplementary material, which is available to authorized users.
Monthly Weather Review, Sep 1, 1981
Interannual hydroclimatic variability and the 2009–2011 extreme ENSO phases in Colombia: from Andean glaciers to Caribbean lowlands
Theoretical and Applied Climatology, Mar 19, 2018
During 2009–2011, Colombia experienced extreme hydroclimatic events associated with the extreme p... more During 2009–2011, Colombia experienced extreme hydroclimatic events associated with the extreme phases of El Niño–Southern Oscillation (ENSO). Here, we study the dynamics of diverse land-atmosphere phenomena involved in such anomalous events at continental, regional, and local scales. Standardized anomalies of precipitation, 2-m temperature, total column water (TCW), volumetric soil water (VSW), temperature at 925 hPa, surface sensible heat (SSH), latent heat (SLH), evaporation (EVP), and liquid water equivalent thickness (LWET) are analyzed to assess atmosphere-land controls and relationships over tropical South America (TropSA) during 1986–2013 (long term) and 2009–2011 (ENSO extreme phases). An assessment of the interannual covariability between precipitation and 2-m temperature is performed using singular value decomposition (SVD) to identify the dominant spatiotemporal modes of hydroclimatic variability over the region’s largest river basins (Amazon, Orinoco, Tocantins, Magdalena-Cauca, and Essequibo). ENSO, its evolution in time, and strong and consistent spatial structures emerge as the dominant mode of variability. In situ anomalies during both extreme phases of ENSO 2009–2011 over the Magdalena-Cauca River basins are linked at the continental scale. The ENSO-driven hydroclimatic effects extend from the diurnal cycle to interannual timescales, as reflected in temperature data from tropical glaciers and the rain-snow boundary in the highest peaks of the Central Andes of Colombia to river levels along the Caribbean lowlands of the Magdalena-Cauca River basin.
Journal of Climate, Jul 15, 2019
Ocean meridional heat transports (MHTs) are deduced as a residual using energy budgets to produce... more Ocean meridional heat transports (MHTs) are deduced as a residual using energy budgets to produce latitude versus time series for the globe, Indo-Pacific, and Atlantic. The top-of-atmosphere (TOA) radiation is combined with the vertically integrated atmospheric energy divergence from atmospheric reanalyses to produce the net surface energy fluxes everywhere. The latter is then combined with estimates of the vertically integrated ocean heat content (OHC) tendency to produce estimates of the ocean heat divergence. Because seasonal sea ice and land runoff effects are not fully considered, the mean annual cycle is incomplete, but those effects are small for interannual variability. However, there is a mismatch between 12-month inferred surface flux and the corresponding OHC changes globally, requiring adjustments to account for the Earth's global energy imbalance. Estimates are greatly improved by building in the constraint that MHT must go to zero at the northern and southern extents of the ocean basin at all times, enabling biases between the TOA and OHC data to be reconciled. Zonal mean global, Indo-Pacific, and Atlantic basin ocean MHTs are computed and presented as 12-month running means and for the mean annual cycle for 2000-16. For the Indo-Pacific, the tropical and subtropical MHTs feature a strong relationship with El Niño-Southern Oscillation (ENSO), and in the Atlantic, MHT interannual variability is significantly affected by and likely influences the North Atlantic Oscillation (NAO). However, Atlantic and Pacific changes are linked, suggesting that the northern annular mode (as opposed to NAO) is predominant. There is also evidence of decadal variability or trends.
Journal of Hydrometeorology, Apr 19, 2017
Intermittency is a core characteristic of precipitation, not well described by data and very poor... more Intermittency is a core characteristic of precipitation, not well described by data and very poorly modeled. Detailed analyses are made of near-global gridded (about 18) hourly or 3-hourly precipitation rates from two updated observational datasets [3-hourly TRMM 3B42, version 7, and hourly CMORPH, version 1.0, bias corrected (CRT)] and from special runs of CESM from January 1998 to December 2013 to obtain hourly values. The analyses explore the intermittency of precipitation: the frequency, intensity, duration, and amounts. A comparison is made for all products using several metrics with a focus on the duration of events, and a new metric is proposed based on the ratio of the frequency of precipitation at certain rates (0.2-2 mm h 21 ) for hourly versus 3-hourly versus daily data. For all seasons and rain rates, TRMM values are similar in pattern to CMORPH, but durations are about 80%-85%. It is mainly over land in the monsoons that CMORPH exceeds TRMM rain durations. Observed duration of precipitation events in CMORPH over oceans are 12-15 h in the tropics and subtropics, much less than the ;20 h for CESM. Hence, the observational results differ somewhat but both are considerably different from the model, which has too much precipitation overall, and it precipitates far too often at low rates and not enough for intense rates, with the divide about 1-2 mm h 21 . There is a need to properly represent precipitation phenomena and processes either explicitly or implicitly (parameterized).
Journal of Climate, Oct 10, 2016
Characteristics of precipitation estimates for rate and amount from three global high-resolution ... more Characteristics of precipitation estimates for rate and amount from three global high-resolution precipitation products (HRPPs), four global climate data records (CDRs), and four reanalyses are compared. All datasets considered have at least daily temporal resolution. Estimates of global precipitation differ widely from one product to the next, with some differences likely due to differing goals in producing the estimates. HRPPs are intended to produce the best snapshot of the precipitation estimate locally. CDRs of precipitation emphasize homogeneity over instantaneous accuracy. Precipitation estimates from global reanalyses are dynamically consistent with the large-scale circulation but tend to compare poorly to rain gauge estimates since they are forecast by the reanalysis system and precipitation is not assimilated. Regional differences among the estimates in the means and variances are as large as the means and variances, respectively. Even with similar monthly totals, precipitation rates vary significantly among the estimates. Temporal correlations among datasets are large at annual and daily time scales, suggesting that compensating bias errors at annual and random errors at daily time scales dominate the differences. However, the signal-to-noise ratio at intermediate (monthly) time scales can be large enough to result in high correlations overall. It is shown that differences on annual time scales and continental regions are around 0.8 mm day 21 , which corresponds to 23 W m 22 . These wide variations in the estimates, even for global averages, highlight the need for better constrained precipitation products in the future.
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Papers by Kevin Trenberth