Satellite‐Observed Vegetation Responses to Intraseasonal Precipitation Variability

Abstract

In recent years there has been substantial interest in improving the skill of subseasonal-to-seasonal (S2S; 2-8 weeks) forecasts, which sit between traditional weather and climate forecasts (Brunet et al., 2010;Vitart et al., 2017). A major source of global S2S predictability is provided by tropical intraseasonal oscillations (ISOs: Ding et al., 2011;Waliser et al., 2003), such as the Madden-Julian Oscillation (MJO), which produces rainfall fluctuations with a period of approximately 30-60 days (Madden & Julian, 1994). Accurate representation of the land surface and its interaction with the atmosphere is also key to developing skillful S2S forecasts. The state of the land surface (e.g., root zone soil moisture or leaf area) varies more slowly than the atmospheric state and affects the partitioning of the surface energy budget through changes in evapotranspiration, surface albedo and roughness. The land therefore provides a potential source of S2S predictability to the atmosphere (Dirmeyer

Surface‐driven amplification of Madden–Julian oscillation circulation anomalies across East Africa and its influence on the Turkana jet

“…Harris et al . (2022) show that vegetation in East Africa responds to intraseasonal (40‐ to 60‐day) precipitation variability with a lag of approximately 15–20 days (Supporting Information Figure S1). We therefore present VOD anomalies averaged 15–20 days after dry and wet MJO days (Figure 2c,f).…”

“…Alongside investigating the surface soil moisture response to MJO-induced precipitation variations, we also analyse VOD anomalies. Harris et al (2022) show that vegetation in East Africa responds to intraseasonal (40-to 60-day) precipitation variability with a lag of approximately 15-20 days (Supporting Information Figure S1). We therefore present VOD anomalies averaged 15-20 days after dry and wet MJO days (Figure 2c,f).…”

“…A substantial amount of this work has focused on the predictability during boreal summer across midlatitude continental regions. There has been somewhat less attention devoted to tropical regions, where atmospheric modes of variability, notably the Madden–Julian oscillation (MJO; Madden and Julian, 1994), drive a large proportion of intraseasonal precipitation variability (Mutai and Ward, 2000; Mpeta and Jury, 2001; Pohl and Camberlin, 2006a; Pohl and Camberlin, 2006b; Berhane and Zaitchik, 2014; Finney et al ., 2020b) and impact surface conditions, including soil moisture (Peng et al ., 2017) and vegetation water content (Harris et al ., 2022). In this study, we explore the potential for intraseasonal land–atmosphere feedbacks in East Africa, where MJO forcing drives strong regional rainfall fluctuations on time‐scales of 30 to 60 days (Pohl and Camberlin, 2006a; Berhane and Zaitchik, 2014).…”

Untangling the importance of dynamic and thermodynamic drivers for wet and dry spells across the Tropical Andes

“…In addition, daily X-band microwave vegetation optical depth (VOD, 0.25 • ) from the global long-term VOD Climate Archive (VODCA) product (Moesinger et al 2020) for 2000-2018 is used to test whether plants respond to the SM fluctuations over spell periods. The VOD product was filtered to remove unphysical day-to-day jumps and vegetation changes associated with surface water dynamics (Harris et al 2022). VOD changes were found to have a close relationship with changes in vegetation water content as well as biomass, where the X-band is the most sensitive to leaf water (c.f.…”

Investigating Diurnal and Seasonal Cycles of Vegetation Optical Depth Retrieved From GNSS Signals in a Broadleaf Forest

“…Understanding the dynamics of water moving through the soil‐plant‐atmosphere continuum is of great importance, as it directly impacts essential physiological processes of photosynthesis and transpiration, ecosystem functioning, and climate regulation (Gentine et al., 2019; Harris et al., 2022; McDowell et al., 2022). The amount of water stored within plants can be a powerful empirical proxy of these processes.…”