Evolution of wet‐day and dry‐day frequency in the western Amazon basin: Relationship with atmospheric circulation and impacts on vegetation

This paper documents the spatio-temporal evolution of wet- and dry-day frequency (WDF and DDF) in the western Amazon, its relationships with oceanic and atmospheric variability and possible impact on vegetation. WDF and DDF changed significantly during the 1980-2009 period (p<0.05). An increase in WDF is observed after 1995 over the northern part of the western Amazon (Maranon basin). The average annual value of WDF changed from 22 days per year before 1995 to 34 days after that date (+55% after 1995). In contrast, DDF increased significantly over the central and southern part of this region (Ucayali basin) after 1986. Average annual DDF was 16.2 days before 1986 and 23.8 days afterwards (+47% after 1986). Interannual variability in WDF appears to be modulated by changes in Pacific SST and the Walker cell during the November-to-March season. This mechanism enhances convective activity over the northern part of the western Amazon. The increase in DDF is related to warming of the North Tropical Atlantic SST, which produces changes in the Hadley cell and subsidence over the central and the southern western Amazon. More intense seasonal hydrological extremes in the western Amazon therefore appear to be related to changes in WDF and DDF that occurred in 1995 and 1986, respectively. During the 2001-2009 period, an index of vegetation condition (NDVI) appears negatively correlated with DDF (r=-0.95; p<0.0001). This suggests that vegetation in the western Amazon is mainly water-limited, rather than light-limited, and indicates that the vegetation is highly sensitive to concentration of rainfall. This article is protected by copyright. All rights reserved.

[1]  D. Bonal,et al.  The response of tropical rainforests to drought—lessons from recent research and future prospects , 2015, Annals of Forest Science.

[2]  S. Ganguly,et al.  Amazon forests did not green‐up during the 2005 drought , 2009 .

[3]  E. Davidson,et al.  Abrupt increases in Amazonian tree mortality due to drought–fire interactions , 2014, Proceedings of the National Academy of Sciences.

[4]  C. Jones,et al.  Climatology of Tropical Intraseasonal Convective Anomalies: 1979–2002 , 2004 .

[5]  R. Dickinson,et al.  Increased dry-season length over southern Amazonia in recent decades and its implication for future climate projection , 2013, Proceedings of the National Academy of Sciences.

[6]  J. Terborgh,et al.  Drought Sensitivity of the Amazon Rainforest , 2009, Science.

[7]  Byron D. Tapley,et al.  The 2009 exceptional Amazon flood and interannual terrestrial water storage change observed by GRACE , 2010 .

[8]  Thomas Hilker,et al.  On the measurability of change in Amazon vegetation from MODIS , 2015 .

[9]  C. Prigent,et al.  Discharge simulation in the sub-basins of the Amazon using ORCHIDEE forced by new datasets , 2011 .

[10]  Jin Chen,et al.  A simple method for reconstructing a high-quality NDVI time-series data set based on the Savitzky-Golay filter , 2004 .

[11]  S. Ganguly,et al.  Widespread decline in greenness of Amazonian vegetation due to the 2010 drought , 2011 .

[12]  L. Verchot,et al.  Decadal covariability of Atlantic SSTs and western Amazon dry‐season hydroclimate in observations and CMIP5 simulations , 2015 .

[13]  Yann L'hote,et al.  Evolution du débit de l’Amazone à Óbidos de 1903 à 1999 / Evolution of the River Amazon’s discharge at Óbidos from 1903 to 1999 , 2004 .

[14]  M. Dettinger,et al.  The key role of dry days in changing regional climate and precipitation regimes , 2014, Scientific Reports.

[15]  A. Manzi,et al.  Moisture source for the Amazon Basin: a study of contrasting years , 2012, Theoretical and Applied Climatology.

[16]  Ajit Subramaniam,et al.  Causes and impacts of the 2005 Amazon drought , 2008 .

[17]  J. Marengo,et al.  Two Contrasting Severe Seasonal Extremes in Tropical South America in 2012: Flood in Amazonia and Drought in Northeast Brazil , 2013 .

[18]  M. Lapointe,et al.  Amazon river flow regime and flood recessional agriculture: Flood stage reversals and risk of annual crop loss , 2016 .

[19]  D. Labat,et al.  Trends in rainfall and temperature in the Peruvian Amazon–Andes basin over the last 40 years (1965–2007) , 2012 .

[20]  Saulo Rodrigues-Filho,et al.  Rainfall patterns in the Southern Amazon: a chronological perspective (1971–2010) , 2015, Climatic Change.

[21]  J. Marengo,et al.  The drought of 2010 in the context of historical droughts in the Amazon region , 2011 .

[22]  Antônio M. T. Ramos,et al.  Do the recent severe droughts in the Amazonia have the same period of length? , 2015, Climate Dynamics.

[23]  C. Tucker,et al.  Vegetation dynamics and rainfall sensitivity of the Amazon , 2014, Proceedings of the National Academy of Sciences.

[24]  Zbigniew W. Kundzewicz,et al.  Change detection in hydrological records—a review of the methodology / Revue méthodologique de la détection de changements dans les chroniques hydrologiques , 2004 .

[25]  Thomas M. Smith,et al.  Improved Global Sea Surface Temperature Analyses Using Optimum Interpolation , 1994 .

[26]  Ning Zeng,et al.  An Atlantic influence on Amazon rainfall , 2010 .

[27]  R. DeFries,et al.  The Amazon basin in transition , 2012, Nature.

[28]  J. Marengo,et al.  Extreme seasonal droughts and floods in Amazonia: causes, trends and impacts , 2015 .

[29]  B. Holben.  Characteristics of maximum-value composite images from temporal AVHRR data , 1986 .

[30]  Luiz E. O. C. Aragão,et al.  Can MODIS EVI monitor ecosystem productivity in the Amazon rainforest? , 2014 .

[31]  Lei Yin,et al.  What controls the interannual variation of the wet season onsets over the Amazon? , 2014 .

[32]  C. Frankenberg,et al.  Forest productivity and water stress in Amazonia: observations from GOSAT chlorophyll fluorescence , 2013, Proceedings of the Royal Society B: Biological Sciences.

[33]  Y. Shimabukuro,et al.  Spatial patterns and fire response of recent Amazonian droughts , 2007 .

[34]  M. Lengaigne,et al.  Large-scale circulation patterns and related rainfall in the Amazon Basin: a neuronal networks approach , 2011, Climate Dynamics.

[35]  J. Espinoza,et al.  Climate variability and extreme drought in the upper Solimões River (western Amazon Basin): Understanding the exceptional 2010 drought , 2011 .

[36]  J. Terborgh,et al.  Long-term decline of the Amazon carbon sink , 2015, Nature.

[37]  Maisa Rojas,et al.  A correlated shortening of the North and South American monsoon seasons in the past few decades , 2015, Climate Dynamics.

[38]  A. Manzi,et al.  A quick look at the 2012 record flood in the Amazon Basin , 2013 .

[39]  Philippe Ciais,et al.  Projected strengthening of Amazonian dry season by constrained climate model simulations , 2015 .

[40]  Frédéric Frappart,et al.  The Major Floods in the Amazonas River and Tributaries (Western Amazon Basin) during the 1970–2012 Period: A Focus on the 2012 Flood , 2013 .

[41]  C. Jones,et al.  Projections of climate change effects on discharge and inundation in the Amazon basin , 2016, Climatic Change.

[42]  D. Nepstad,et al.  Amazon drought and its implications for forest flammability and tree growth: a basin‐wide analysis , 2004 .

[43]  R. Nemani,et al.  Persistent effects of a severe drought on Amazonian forest canopy , 2012, Proceedings of the National Academy of Sciences.

[44]  A. Grimm,et al.  Interdecadal Variability of the South American Precipitation in the Monsoon Season , 2015 .

[45]  Dong Eun Lee,et al.  North Tropical Atlantic influence on western Amazon fire season variability , 2011 .

[46]  B. Liebmann,et al.  Description of a complete (interpolated) outgoing longwave radiation dataset , 1996 .

[47]  A. Huete,et al.  Amazon Forests Green-Up During 2005 Drought , 2007, Science.

[48]  Philippe Ciais,et al.  Future changes in precipitation and impacts on extreme streamflow over Amazonian sub-basins , 2013 .

[49]  J. Taupin,et al.  Analysis of the climate controls on the isotopic composition of precipitation (δ18O) at Nuevo Rocafuerte, 74.5°W, 0.9°S, 250 m, Ecuador , 2008 .

[50]  David J. Harding,et al.  Amazon forests maintain consistent canopy structure and greenness during the dry season , 2014, Nature.

[51]  A. Huete,et al.  Overview of the radiometric and biophysical performance of the MODIS vegetation indices , 2002 .

[52]  D. Roy,et al.  Large seasonal swings in leaf area of Amazon rainforests , 2007, Proceedings of the National Academy of Sciences.

[53]  A. Huete,et al.  Amazon rainforests green‐up with sunlight in dry season , 2006 .

[54]  Oliver L. Phillips,et al.  Intensification of the Amazon hydrological cycle over the last two decades , 2013 .

[55]  A. Pettitt.  A Non‐Parametric Approach to the Change‐Point Problem , 1979 .

[56]  C. Ropelewski,et al.  Shifts in the Statistics of Daily Rainfall in South America Conditional on ENSO Phase , 2008 .

[57]  C. Nobre,et al.  Climate change consequences on the biome distribution in tropical South America , 2007 .

[58]  Josyane Ronchail,et al.  The extreme 2014 flood in south-western Amazon basin: the role of tropical-subtropical South Atlantic SST gradient , 2014 .

[59]  Juan Carlos Castilla-Rubio,et al.  Land-use and climate change risks in the Amazon and the need of a novel sustainable development paradigm , 2016, Proceedings of the National Academy of Sciences.

[60]  D. Labat,et al.  Contrasting regional discharge evolutions in the Amazon basin (1974–2004) , 2009 .

[61]  R. Reynolds,et al.  The NCEP/NCAR 40-Year Reanalysis Project , 1996, Renewable Energy.

[62]  P. Atkinson,et al.  Amazon vegetation greenness as measured by satellite sensors over the last decade , 2011 .

[63]  J. Ronchail,et al.  Spatio‐temporal rainfall variability in the Amazon basin countries (Brazil, Peru, Bolivia, Colombia, and Ecuador) , 2009 .

[64]  Josyane Ronchail,et al.  Rainfall hotspots over the southern tropical Andes: Spatial distribution, rainfall intensity, and relations with large‐scale atmospheric circulation , 2015 .

[65]  George N. Kiladis,et al.  Submonthly Convective Variability over South America and the South Atlantic Convergence Zone , 1999 .

[66]  C. Nobre,et al.  The Drought of Amazonia in 2005 , 2008 .

[67]  Philippe Vauchel,et al.  From drought to flooding: understanding the abrupt 2010–11 hydrological annual cycle in the Amazonas River and tributaries , 2012 .