Frequency and distribution of winter melt events from passive microwave satellite data in the pan-Arctic, 1988–2013
This study presents an algorithm for detecting winter melt events in seasonal snow cover based on temporal variations in the brightness temperature difference between 19 and 37 GHz from satellite passive microwave measurements. An advantage of the passive microwave approach is that it is based on th...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-11-01
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| Series: | The Cryosphere |
| Online Access: | http://www.the-cryosphere.net/10/2589/2016/tc-10-2589-2016.pdf |
| Summary: | This study presents an algorithm for detecting winter melt events in seasonal
snow cover based on temporal variations in the brightness temperature
difference between 19 and 37 GHz from satellite passive microwave
measurements. An advantage of the passive microwave approach is that it is
based on the physical presence of liquid water in the snowpack, which may not
be the case with melt events inferred from surface air temperature data. The
algorithm is validated using in situ observations from weather stations, snow
pit measurements, and a surface-based passive microwave radiometer. The
validation results indicate the algorithm has a high success rate for melt
durations lasting multiple hours/days and where the melt event is preceded by
warm air temperatures. The algorithm does not reliably identify
short-duration events or events that occur immediately after or before
periods with extremely cold air temperatures due to the thermal inertia of
the snowpack and/or overpass and resolution limitations of the satellite
data. The results of running the algorithm over the pan-Arctic region (north
of 50° N) for the 1988–2013 period show that winter melt events are
relatively rare, totaling less than 1 week per winter over most areas, with
higher numbers of melt days (around two weeks per winter) occurring in more
temperate regions of the Arctic (e.g., central Québec and Labrador,
southern Alaska and Scandinavia). The observed spatial pattern is similar to
winter melt events inferred with surface air temperatures from the
ERA-Interim (ERA-I) and Modern Era-Retrospective Analysis for Research and
Applications (MERRA) reanalysis datasets. There was little evidence of trends
in winter melt event frequency over 1988–2013 with the exception of negative
trends over northern Europe attributed to a shortening of the duration of the
winter period. The frequency of winter melt events is shown to be strongly
correlated to the duration of winter period. This must be taken into account
when analyzing trends to avoid generating false positive trends from shifts
in the timing of the snow cover season. |
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| ISSN: | 1994-0416 1994-0424 |