Data from: Snow-cover seasonality in Kyrgyzstan: Variation and change over 20 years (2001-2021) as observed by the MODIS Terra snow product

Snow seasonality is expected to change as a result of planetary warming.
Yet, how the timings of snow seasons have already shifted in mountain
environments can be counterintuitive. Here, we updated our 2018 analyses
of snow seasonality in Kyrgyzstan (KG) using more data and improved
methods. Using two decades of MODIS snow-cover data, we investigated
trends in four snow seasonality metrics: First Date of Snow (FDoS); Last
Date of Snow (LDoS); Duration of the Snow Season (DoSS); and Snow-Covered
Days (SCD). Our novel but conservative nonparametric approach analyzed
trends within elevation ranges at two administrative levels: oblast and
rayon. To attenuate the risk of false-positive trends, we reported as
“notable” only those significant (p<0.05) nonparametric trends that
were also (i) strongly asymmetric (at least twice as many significant
pixels in one direction) within a elevational range of the oblast or rayon
and (ii) covering at least 5% of the elevation range in oblast or rayon
and more than 10 pixels. We used both simple and advanced snow-cover
metrics, with the latter exploiting the within-composite chronobyte detail
available in the MOD10A2.061 product. We found notable trends to earlier
FDoS below 3000 m in western KG and more SCD between 1500-3500 m
 in western KG. We also found the expected notable trends towards
earlier LDoS at both oblast and rayon levels. In northwestern KG, DoSS was
notably longer <3000 m, but notably shorter at 3500-4000 m. In our
2018 analyses, we found at the national level 160% more area trending to
earlier FDoS than to earlier LDoS. Our comprehensive updated trend
analysis was designed to be more conservative. It revealed more area
(106-130%) trending to earlier FDoS than earlier LDoS, reinforcing the
counterintuitive finding of longer snow seasons starting earlier at lower
elevations.