Satellite‐Observed Vegetation Responses to Intraseasonal Precipitation Variability. Issue 15 (9th August 2022)

• Record Type: Journal Article
• Authors: Harris, Bethan L.; Taylor, Christopher M.; Weedon, Graham P.; Talib, Joshua; Dorigo, Wouter; van der Schalie, Robin
• Is Part Of: Geophysical research letters. Volume 49:Issue 15(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-09
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL099635
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: There is limited understanding of how vegetation responds to intraseasonal modes of rainfall variability despite their importance in many tropical regions. We use observations of precipitation and X‐band Vegetation Optical Depth (VOD) from 2000 to 2018 to assess the relationships between rainfall and vegetation water content on 25–60‐day timescales. Cross‐spectral analysis identifies coherent intraseasonal relationships between precipitation and VOD, mostly in arid or semi‐arid regions where vegetation is water‐limited. Changes in VOD tend to lag anomalous rainfall, usually within 7 days. The fastest vegetation response is observed in sparsely vegetated areas (median 3 days). Following strong intraseasonal wet events, anomalously high VOD can persist for 2 months after the rainfall peak. This vegetation response can feed back onto the atmosphere, so improved representation of vegetation responses in models has the potential to improve subseasonal‐to‐seasonal forecasts. Plain Language Summary: It is difficult to predict temperature and rainfall more than 2 weeks in advance. Predictions at this timescale are helped by some common patterns of rainfall which cause wet and dry spells lasting from a few weeks to 2 months. Here, we use satellite measurements of rainfall and a vegetation metric that is strongly related to vegetation water content to study the relationships between these rainfall patterns and vegetation across the world. We find many regions where increased rainfall is followed by an increase in vegetation water content, usually with a delay of less than a week. This is most commonly seen in drier locations, where vegetation has a limited supply of water. After a wet spell, vegetation water content can persist above normal levels for over 2 months. This means that changes in vegetation caused by a wet or dry spell have the potential to affect rainfall in the next wet or dry spell, via changes in the energy and water transfers between the land and the atmosphere. Therefore, representing these vegetation responses correctly in models may lead to improvements in temperature and rainfall prediction weeks ahead. Key Points: Vegetation Optical Depth responds to intraseasonal precipitation variability in arid and semi‐arid regions The phase difference of this response is usually less than 7 days, and is shortest for sparse vegetation After a wet intraseasonal period, the vegetation response can persist for over 2 months