Near-surface temperature inversion during summer at Summit, Greenland, and its relation to MODIS-derived surface temperatures
As rapid warming of the Arctic occurs, it is imperative that climate indicators such as temperature be monitored over large areas to understand and predict the effects of climate changes. Temperatures are traditionally tracked using in situ 2 m air temperatures and can also be assessed using rem...
Main Authors: | , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-03-01
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Series: | The Cryosphere |
Online Access: | https://www.the-cryosphere.net/12/907/2018/tc-12-907-2018.pdf |
Summary: | As rapid warming of the Arctic occurs, it is imperative that climate
indicators such as temperature be monitored over large areas to understand
and predict the effects of climate changes. Temperatures are traditionally
tracked using in situ 2 m air temperatures and can also be assessed using
remote sensing techniques. Remote sensing is especially valuable over the
Greenland Ice Sheet, where few ground-based air temperature measurements
exist. Because of the presence of surface-based temperature inversions in
ice-covered areas, differences between 2 m air temperature and the
temperature of the actual snow surface (referred to as <q>skin</q> temperature)
can be significant and are particularly relevant when considering validation
and application of remote sensing temperature data. We present results from
a field campaign extending from 8 June to 18 July 2015, near Summit
Station in Greenland, to study surface temperature using the following
measurements: skin temperature measured by an infrared (IR) sensor, 2 m air
temperature measured by a National Oceanic and Atmospheric Administration
(NOAA) meteorological station, and a Moderate Resolution Imaging Spectroradiometer (MODIS) surface temperature product. Our data indicate
that 2 m air temperature is often significantly higher than snow skin
temperature measured in situ, and this finding may account for apparent
biases in previous studies of MODIS products that used 2 m air temperature
for validation. This inversion is present during our study period when
incoming solar radiation and wind speed are both low. As compared to our in
situ IR skin temperature measurements, after additional cloud masking, the
MOD/MYD11 Collection 6 surface temperature standard product has an RMSE of
1.0 °C and a mean bias of −0.4 °C, spanning a range of
temperatures from −35 to −5 °C (RMSE =
1.6 °C and mean bias = −0.7 °C prior to cloud
masking). For our study area and time series, MODIS surface temperature
products agree with skin surface temperatures better than previous studies
indicated, especially at temperatures below −20 °C, where other
studies found a significant cold bias. We show that the apparent cold
bias present in other comparisons of 2 m air temperature and MODIS surface
temperature may be a result of the near-surface temperature inversion.
Further investigation of how in situ IR skin temperatures compare to MODIS
surface temperature at lower temperatures (below −35 °C) is
warranted to determine whether a cold bias exists for those temperatures. |
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ISSN: | 1994-0416 1994-0424 |