On the Relevance of Aerosols to Snow Cover Variability Over High Mountain Asia

Abstract

While meteorology and aerosols are identified as key drivers of snow cover (SC) variability in High Mountain Asia, complex non‐linear interactions between them are not adequately quantified. Here, we attempt to unravel these interactions through a simple relative importance (RI) analysis of meteorological and aerosol variables from ERA5/CAMS‐EAC4 reanalysis against satellite‐derived SC from Moderate Resolution Imaging Spectroradiometer across 2003–2018. Our results show a statistically significant 7% rise in the RI of aerosol‐meteorology interactions (AMI) in modulating SC during late snowmelt season (June and July), notably over low snow‐covered (LSC) regions. Sensitivity tests further reveal that the importance of meteorological interactions with individual aerosol species are more prominent than total aerosols over LSC regions. We find that the RI of AMI for LSC regions is clearly dominated by carbonaceous aerosols, on top of the expected importance of dynamic meteorology. These findings clearly highlight the need to consider AMI in hydrometeorological monitoring, modeling, and reanalyses.

Instant Response of Tibetan Plateau Surface Albedo to Snow Coverage and Depth in Snow Season

“…First, the intra‐seasonal variations of atmospheric circulation modulate the water vapor transport from South and Central Asia, which in turn affects the snowfall over the TP (Song et al., 2019). Second, the widespread shallow snow over the TP has a low albedo, and it will be further reduced by the aerosol and dust in snow and snow aging (Roychoudhury et al., 2022; Sarangi et al., 2020; Zhang et al., 2018). The low snow albedo brings accelerated snowmelt through “snow‐albedo” positive feedback, and this is the main pathway that snow depth affects surface albedo changes.…”

“…Conversely, in central and eastern TP, the widespread shallow snow has a short duration due to its relatively low albedo (Flanner & Zender, 2005; Liu et al., 2021, 2022; Wang et al., 2020). In addition, the existence of light‐absorbing aerosols in snow can also lead to reduced albedo and accelerated snowmelt (Gul et al., 2021; Lee et al., 2017; Li et al., 2022; Roychoudhury et al., 2022). These researches indicate that snow elements that dominate changes of surface albedo may differ in different regions of the TP, and the influence of snow depth (SD) cannot be ignored.…”

Reducing the Cold Bias of the WRF Model Over the Tibetan Plateau by Implementing a Snow Coverage‐Topography Relationship and a Fresh Snow Albedo Scheme

“…Thus, this value is specifically applicable to the TP, but needs adjustment when applied to other regions. Such a setting for α min can directly consider the snow darkening effect of aerosols, which is specifically important for the study region (Gul et al., 2022; He et al., 2018; Roychoudhury et al., 2022).…”

“…Compared to the CLASS scheme, there are two advantages. One is that this scheme considers snow contamination in snow aging parameterization, because dust and black carbon can significantly reduce the snow albedo (He et al., 2019b; Roychoudhury et al., 2022) especially in the study region. The other is that this scheme parameterizes the albedo of fresh shallow snow instead of only providing a constant value.…”

Unraveling the Complexities of Aerosol-Meteorology Interactions on Snowmelt in High Mountain Asia

“…The lack of consistent geophysical observations across regions like HMA, partly driven by its remoteness and complex terrain, requires the use of reanalysis products such as ERA5/CAMS-EAC4 and MERRA-2 that provide an opportunity for understanding long-term changes in HMA. In a recent study, we attempted to address AMI by quantifying the importance of second-order interactions between aerosol and meteorological variables from ERA5/CAMS-EAC4 reanalysis to satellite-based MODIS SCF using a linear regression model 44 (hereafter as R22). Our ndings show that AMI, particularly those related to carbonaceous aerosols, holds high importance for glacial regions with low snow cover (LSC) in HMA, particularly during the late snowmelt season (May-July).…”