Physical and Environmental Geography | Open Access Articles

Sequias En El Sur De La Peninsula De Yucatan: Analisis De La Variabilidad Anual Y Estacional De La Precipitacion (Droughts In The Southern Yucatan Peninsula: Analysis Of The Annual And Seasonal Precipitation Variability), Sofia Mardero, Elsa Nickl, Birgit Schmook, Laura Schneider, John Rogan, Zachary Christman, Deborah Lawrence

Zachary Christman

Paper is in Spanish. English abstract: This study analyzes the spatial and temporal variability of precipitation across the Southern Yucatán Peninsula in Mexico, addressing the anomalies and trends of annual and seasonal precipitation as well as the occurrence of meteorological droughts, using rainfall data from nine weather stations during the period 1953-2007. Linear regression in the annual and seasonal rainfall were used to analyze the increase or decrease in precipitation trends over this period. Precipitation anomalies enabled the evaluation of the stability, deficit, or surplus of precipitation for each year or season, and a quintile method was used to …

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Reanalysis Data Underestimate Significant Changes In Growing Season Weather In Kazakhstan, C. K. Wright, K. M. De Beurs, Z. K. Akhmadiyeva, P. Y. Groisman, G. M. Henebry

Geoffrey Henebry

We present time series analyses of recently compiled climate station data which allowed us to assess contemporary trends in growing season weather across Kazakhstan as drivers of a significant decline in growing season normalized difference vegetation index (NDVI) recently observed by satellite remote sensing across much of Central Asia. We used a robust nonparametric time series analysis method, the seasonal Kendall trend test to analyze georeferenced time series of accumulated growing season precipitation (APPT) and accumulated growing degree-days (AGDD). Over the period 2000–2006 we found geographically extensive, statistically significant (p < 0.05) decreasing trends in APPT and increasing trends in AGDD. The temperature trends were especially apparent during the warm season and coincided with precipitation decreases in northwest Kazakhstan, indicating that pervasive drought conditions and higher temperature excursions were the likely drivers of NDVI declines observed in Kazakhstan over the same period. We also compared the APPT and AGDD trends at individual stations with results from trend analysis of gridded monthly precipitation data from the Global Precipitation Climatology Centre (GPCC) Full Data Reanalysis v4 and gridded daily near surface air temperature from the National Centers for Climate Prediction Reanalysis v2 (NCEP R2). We found substantial deviation between the station and the reanalysis trends, suggesting that GPCC and NCEP data substantially underestimate the geographic extent of recent drought in Kazakhstan. Although gridded climate products offer many advantages in ease of use and complete coverage, our findings for Kazakhstan should serve as a caveat against uncritical use of GPCC and NCEP reanalysis data and demonstrate the importance of compiling and standardizing daily climate data from data-sparse regions like Central Asia.

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Dual Scale Trend Analysis Distinguishes Climatic From Anthropogenic Effects On The Vegetated Land Surface, K. M. De Beurs, C. K. Wright, G. M. Henebry

Geoffrey Henebry

We present a dual scale trend analysis for characterizing and comparing two contrasting areas of change in Russia and Kazakhstan that lie less than 800 km apart. We selected a global NASA MODIS (moderate resolution imaging spectroradiometer) product (MCD43C4 and MCD43A4) at a 0.05◦ (∼5.6 km) and 500 m spatial resolution and a 16-day temporal resolution from 2000 to 2008. We applied a refinement of the seasonal Kendall trend method to the normalized difference vegetation index (NDVI) image series at both scales. We only incorporated composites during the vegetative growing season which was delineated by start of season and end …

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Zachary Christman

Reanalysis Data Underestimate Significant Changes In Growing Season Weather In Kazakhstan, C. K. Wright, K. M. De Beurs, Z. K. Akhmadiyeva, P. Y. Groisman, G. M. Henebry

Geoffrey Henebry

Dual Scale Trend Analysis Distinguishes Climatic From Anthropogenic Effects On The Vegetated Land Surface, K. M. De Beurs, C. K. Wright, G. M. Henebry

Geoffrey Henebry