Changing snow seasonality in the highlands of Kyrgyzstan

Monika A Tomaszewska,Geoffrey M Henebry

doi:10.1088/1748-9326/aabd6f

Monika A Tomaszewska, Geoffrey M Henebry

Open Access

https://doi.org/10.1088/1748-9326/aabd6f

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Abstract

Few studies have examined changing snow seasonality in Central Asia. Here, we analyzed changes in the seasonality of snow cover across Kyrgyzstan (KGZ) over 14 years from 2002/03–2015/16 using the most recent version (v006) of MODIS Terra and Aqua 8 day snow cover composites (MOD10A2/MYD10A2). We focused on three metrics of snow seasonality—first date of snow, last date of snow, and duration of snow season—and used nonparametric trends tests to assess the significance and direction of trends. We evaluated trends at three administration scales and across elevation. We used two techniques to assure that our identification of significant trends was not resulting from random spatial variation. First, we report only significant trends (positive or negative) that are at least twice as prevalent as the converse trends. Second, we use a two-stage analysis at the national scale to identify asymmetric directional changes in snow seasonality. Results show that more territory has been experiencing earlier onset of snow than earlier snowmelt, and roughly equivalent areas have been experiencing longer and shorter duration of snow seasons in the past 14 years. The changes are not uniform across KGZ, with significant shifts toward earlier snow arrival in western and central KGZ and significant shifts toward earlier snowmelt in eastern KGZ. The duration of the snow season has significantly shortened in western and eastern KGZ and significantly lengthened in northern and southwestern KGZ. Duration is significantly longer where the snow onset was significantly earlier or the snowmelt significantly later. There is a general trend of significantly earlier snowmelt below 3400 m and the area of earlier snowmelt is 15 times greater in eastern than western districts. Significant trends in the Aqua product were less prevalent than in the Terra product, but the general trend toward earlier snowmelt was also evident in Aqua data.

Highlights

Snow cover extent has been observed to be changing for more than three decades using both in-situ data (Groisman et al 2006, Bulygina et al 2010, 2011) and remote sensing products (Schanda et al 1983, Hall et al 2002, Brown and Robinson 2011)
Earlier snow arrival corresponds to a negative trend in the first date of snow (FDoS), and it appears prevalent across Kyrgyzstan (figure 1(b)), in the oblasts of Chuy (2079 km2), Jalal-Abad (1534 km2) and Osh (2021 km2), for almost 8000 km2 in total
Earlier snowmelt corresponds to a negative trend in the last date of snow (LDoS), and it appears prevalent across Kyrgyzstan (figure 1(c)), in the oblasts of Naryn (2227 km2) and Issyk-Kul (1376 km2), for almost 5000 km2 in total

Summary

Introduction

Snow cover extent has been observed to be changing for more than three decades using both in-situ data (Groisman et al 2006, Bulygina et al 2010, 2011) and remote sensing products (Schanda et al 1983, Hall et al 2002, Brown and Robinson 2011). Studies in montane Central Asia are relatively few, especially at higher spatial resolutions, but they have all shown significant changes, whether in snow cover (Dietz et al 2013, 2014, Zhou et al 2013, Tang et al 2017), glacial extent (Aizen et al 1995, Narama et al 2010), or meltwater runoff (Aizen et al 1997, Chevallier et al 2014). There is a notable paucity of studies on the changing environment across montane Central Asia (Hijioka et al 2014, Reyer et al 2017)

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