Elsa Nickl

Teleconnections and climate in the Peruvian Andes

Changes in Annual Land-Surface Precipitation Over the Twentieth and Early Twenty-First Century

Time trends in annual land-surface precipitation during the twentieth and early twenty-first cent... more Time trends in annual land-surface precipitation during the twentieth and early twenty-first centuries and their spatial patterns are estimated from gridded (at a 0.5 ◦ × 0.5 ◦ spatial resolution) rain-gauge-based precipitation data sets available from the Climatic Research Unit (CRU), the Global Precipitation Climatology Centre (GPCC), and at the University of Delaware (UDel). Our analyses of these precipitation data sets make use of spatially weighted (geographic) percentiles as well as of join-point and simple linear regression. A consistent increase in annual land-surface-average precipitation (of approximately 0.2 and 0.5 mm/year) occurred during the first half of the twentieth century. This increase was followed by nearly a half-century (approximately forty-four years, from 1949 through 1993) of decreases in annual land-surface-average precipitation (on the order of 0.3 to 0.6mm/year). Trends, once again, reversed themselves in the early 1990s and increased (at rates of approx...

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VARIABILITY AND CLIMATE CHANGE IN THE CENTRAL PERUVIAN ANDES

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Advances in Geosciences, 2008

The relationship between monthly mean sea surface temperature (SST) anomalies in the commonly use... more The relationship between monthly mean sea surface temperature (SST) anomalies in the commonly used El Niño regions and precipitation for 44 stations in Perú is documented for 1950-2002. Linear lag correlation analysis is employed to establish the potential for statistical precipitation forecasts from SSTs. Useful monthly mean precipitation anomaly forecasts are possible for several locations and calendar months if SST anomalies in El Niño 1+2, Niño 3.4, and Niño 4 regions are available. Prediction of SST anomalies in El Niño regions is routinely available from Climate Prediction Center, NOAA, with reasonable skill in the El Niño 3.4 region, but the prediction in El Niño 1+2 region is less reliable. The feasibility of using predicted SST anomalies in the El Niño 3.4 region to predict SST anomalies in El Niño 1+2 region is discussed.

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Mesoscale Simulations of the Land Surface Effects of Historical Logging in a Moist Continental Climate Regime

... Nicholas P. Klingaman,* Jason Butke, Daniel J. Leathers, Kevin R. Brinson, and Elsa Nickl ...... more

Mesoscale Simulations of the Land Surface Effects of Historical Logging in a Moist Continental Climate Regime

Journal of Applied Meteorology and Climatology, 2008

... Nicholas P. Klingaman,* Jason Butke, Daniel J. Leathers, Kevin R. Brinson, and Elsa Nickl ...... more

Mapping seasonal trends in vegetation using AVHRR-NDVI time series in the Yucatán Peninsula, Mexico

This research examines the spatio-temporal trends in Advanced Very High Resolution Radiometer (AV... more This research examines the spatio-temporal trends in Advanced Very High Resolution Radiometer (AVHRR) Global Inventory Modelling and Mapping Studies (GIMMS) normalized difference vegetation index (NDVI) time series to ascribe land use change and precipitation to observed changes in land cover from 1982 to 2007 in the Mexican Yucatán Peninsula, using seasonal trend analysis (STA). In addition to discrete land cover transitions across the study region, patterns of agricultural intensification, urban expansion and afforestation in protected areas have enacted changes to the seasonal patterns of apparent greenness observed through STA greenness parameters. The results indicate that the seasonal variation in NDVI can be used to distinguish among different land cover transitions, and the primary differences among these transitions were in changes in overall greenness, peak annual greenness and the timing of the growing season. Associations between greenness trends and precipitation were weak, indicating a human-dominated system for the 26 years examined. Changes in the states of Campeche, Quintana Roo and Yucatán appear to be associated with pasture cultivation, urban expansion-extensive cultivation and urban expansion-intensive cultivation, respectively.

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Changes in Annual Land-Surface Precipitation Over the Twentieth and Early Twenty-First Century

Annals of The Association of American Geographers, 2010

Time trends in annual land-surface precipitation during the twentieth and early twenty-first cent... more Time trends in annual land-surface precipitation during the twentieth and early twenty-first centuries and their spatial patterns are estimated from gridded (at a 0.5° × 0.5° spatial resolution) rain-gauge-based precipitation data sets available from the Climatic Research Unit (CRU), the Global Precipitation Climatology Centre (GPCC), and at the University of Delaware (UDel). Our analyses of these precipitation data sets make use of spatially weighted (geographic) percentiles as well as of join-point and simple linear regression. A consistent increase in annual land-surface-average precipitation (of approximately 0.2 and 0.5 mm/year) occurred during the first half of the twentieth century. This increase was followed by nearly a half-century (approximately forty-four years, from 1949 through 1993) of decreases in annual land-surface-average precipitation (on the order of 0.3 to 0.6 mm/year). Trends, once again, reversed themselves in the early 1990s and increased (at rates of approximately 0.75 to 2.1 mm/year) over the decade from 1992 through 2002. Maps of precipitation change during these alternating periods of increasing and decreasing precipitation show considerable spatial variability. Las tendencias temporales en precipitación anual sobre el terreno durante el siglo XX y comienzos del XI y sus patrones espaciales están calculados a partir de conjuntos de datos de precipitación basados en registros pluviométricos distribuidos en cuadrícula (a 0.5° x 0.5° de resolución espacial), disponibles en la Unidad de Investigación Climática (CRU, sigla en inglés), el Centro de Climatología para la Precipitación Global (GPCC) y la Universidad de Delaware (UDel). Nuestros análisis de estos conjuntos de datos de precipitación utilizan percentiles espacialmente ponderados (geográficos), lo mismo que regresiones join-point y linear simple. Se presentó un consistente incremento de la precipitación promedio anual sobre el terreno (de aproximadamente 0.2 y 0.5 mm/año) durante la primera mitad del siglo XX. A tal incremento siguió un período de cerca de medio siglo (aproximadamente cuarenta y cuatro años, de 1949 a 1993) de disminución de la precipitación promedio anual sobre el terreno (del orden de 0.3 a 0.6 mm/año). Nuevamente las tendencias se reversaron a sí mismas a principios de los 1990 y se incrementaron (a tasas de aproximadamente 0.75 a 2.1 mm/año) en la década que se extendió de 1992 a 2002. Los mapas del cambio de la precipitación durante estos períodos alternantes de incremento y disminución de la precipitación muestran considerable variabilidad espacial.

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