Arctic nighttime land-surface temperatures derived by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the NASA Terra and Aqua satellites are investigated. We use the local equator crossing ti...Arctic nighttime land-surface temperatures derived by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the NASA Terra and Aqua satellites are investigated. We use the local equator crossing times of 22:30 and 01:30, respectively, in the analysis of changes, trends and variations on the Arctic region and within 120° sectors. We show increases in the number of days above 0°C and significant increase trends over their decadal periods of March 2000 through 2010 (MODIS Terra) and July 2002 through 2012 (MODIS Aqua). The MODIS Aqua nighttime Arctic land-surface temperature change, +0.2°C ± 0.2°C with P-value of 0.01 indicates a reduction relative to the MODIS Terra nighttime Arctic land-surface temperature change, +1.8°C ± 0.3°C with P-value of 0.01. This reduction is a decadal non-stationary component of the Arctic land-surface temperature changes. The reduction is greatest, -1.3°C ± 0.2°C with P-value of 0.01 in the Eastern Russia— Western North American sector of the Arctic during the July 2002 through 2012.展开更多
Across the Arctic changes in active layer, melting of glaciers and ground ice, thawing of permafrost and sequestration changes of carbon storage are driven in part by variations of land surface heat absorption, conduc...Across the Arctic changes in active layer, melting of glaciers and ground ice, thawing of permafrost and sequestration changes of carbon storage are driven in part by variations of land surface heat absorption, conduction and re-radiation relative to solar irradiance. We investigate Arctic land-surface temperature changes and regional variations derived by the MODIS sensors on NASA Aqua and Terra from March 2000 through July 2012. Over this decadal period we detect increase in the number of days with daytime land-surface temperature above 0℃. There are indications of increasing trends of land-surface temperature change. Regional variations of the changes in land-surface temperature likely arise due to surface material types and topography relative to the daytime variation of solar irradiance.展开更多
The diurnal variation of surface temperature is a fundamental parameter as it is a driver of physical processes of atmosphere-land and -ocean energy and mass cycles playing a key role in meteorology and climatology. O...The diurnal variation of surface temperature is a fundamental parameter as it is a driver of physical processes of atmosphere-land and -ocean energy and mass cycles playing a key role in meteorology and climatology. Our investigation focus is on the diurnal variation of land-surface temperature derived by the Moderate Resolution Imaging Spectroradiometer (MODIS) deployed on the NASA Terra and Aqua satellites. We key our investigation on the ascending and descending mode equator crossing times for daytime and nighttime land-surface temperature variations from March 2000 through 2010 (MODIS-Terra) and July 2002 through 2012 (MODIS-Aqua) and assess the diurnal land-surface temperature range changes at those sampling times. Our investigation shows non-stationary changes in the trends of land-surface temperature diurnal range. We identify changes in the diurnal range trends linked to increase of daytime and nighttime land-surface temperatures from March 2000 through 2010 and decrease in daytime and nighttime land-surface temperatures from July 2002 through 2012. The most recent decrease in daytime and nighttime land-surface temperatures and diurnal range will affect Arctic and other associated energy and mass cycles.展开更多
The influences of the wintertime AO (Arctic Oscillation) on the interdecadal variation of summer monsoon rainfall in East Asia were examined. An interdecadal abrupt change was found by the end of the 1970s in the vari...The influences of the wintertime AO (Arctic Oscillation) on the interdecadal variation of summer monsoon rainfall in East Asia were examined. An interdecadal abrupt change was found by the end of the 1970s in the variation of the AO index and the leading principal component time series of the summer rainfall in East Asia. The rainfall anomaly changed from below normal to above normal in central China, the southern part of northeastern China and the Korean peninsula around 1978. However, the opposite interdecadal variation was found in the rainfall anomaly in North China and South China. The interdecadal variation of summer rainfall is associated with the weakening of the East Asia summer monsoon circulation. It is indicated that the interdecadal variation of the AO exerts an influence on the weakening of the monsoon circulation. The recent trend in the AO toward its high-index polarity during the past two decades plays important roles in the land-sea contrast anomalies and wintertime precipitation anomaly. The mid- and high-latitude regions of the Asian continent are warming, while the low-latitude regions are cooling in winter and spring along with the AO entering its high-index polarity after the late 1970s. In the meantime, the precipitation over the Tibetan Plateau and South China is excessive, implying an increase of soil moisture. The cooling tendency of the land in the southern part of Asia will persist until summer because of the memory of soil moisture. So the warming of the Asian continent is relatively slow in summer. Moreover, the Indian Ocean and Pacific Ocean, which are located southward and eastward of the Asian land, are warming from winter to summer. This suggests that the contrast between the land and sea is decreased in summer. The interdecadal decrease of the land-sea heat contrast finally leads to the weakening of the East Asia summer monsoon circulation.展开更多
Using a regional atmospheric model for Arctic climate simulation, two groups of numerical experiments were carried out to study the influence of changes in the underlying surface （land surface, sea surface, and sea i...Using a regional atmospheric model for Arctic climate simulation, two groups of numerical experiments were carried out to study the influence of changes in the underlying surface （land surface, sea surface, and sea ice （LS/SS/SI）） from mild ice years to severe ice years on Arctic climate. In each experiment in the same group, the initial values and lateral boundary conditions were identical. The underlying surface conditions were updated every six hours. The model was integrated for 10 a and monthly mean results were saved for analysis. Variations in annual mean surface air temperature were closely correlated with changes in LS/SS/SI, with a maximum change of more than 15 K. The impact of changes in LS/SS/SI on low-level air temperature was also evident, with significant changes seen over the ocean. However, the maximum change was less than 2 K. For air temperature above 700 hPa, the impact of LS/SS/SI changes was not significant. The distribution of annual mean sea level pressure differences was coincident with the distribution of annual mean sea ice concentration. The difference centers were located in the Barents Sea, the Kara Sea, and the East Siberian Sea, with the maximum value exceeding 3 hPa. For geopotential height, some results passed and some failed a t-test. For results passing the t-test, the area of significance did not decrease with height. There was a significant difference at high levels, with a value of 27 gpm in the difference center at 200 hPa.展开更多
Cape Dyer (DYE-M), located on the easternmost point of Baffin Island, is a former DEW line radar station built in 1956-57 which was upgraded in 1993 as part of the current North Warning System. Environmental studies i...Cape Dyer (DYE-M), located on the easternmost point of Baffin Island, is a former DEW line radar station built in 1956-57 which was upgraded in 1993 as part of the current North Warning System. Environmental studies in the late 1990s and early 2000s determined that extensive soil contamination existed across the site, and excavation of six landfills and subsequent reshaping of the area in 2008 disturbed approximately 19,700 m2. A four-year pilot project was conducted between 2009 and 2012 to investigate feasibility of, and determine methods to, accelerate revegetation of the disturbed area through assisted seed dispersal of native and non native species and selective transplantation of slow-growing shrub species. Prior to revegetation efforts, plant surveys conducted in July 2009 determined that 15 species were present in the undisturbed areas, of which Salix arctica (~11%), Vaccinium uliginosum L. (~8%), and Empetrum nigrum L. (~5%) were the predominant species. A total of 14 species (three new) were observed growing on the disturbed areas between 2010 and 2012. The majority of Lolium multiflorum (annual ryegrass) seeds planted as a nurse species in 2009 grew in 2010, but most were stunted and only observed in furrows or sheltered areas at a low density. Salix arctica Pall. (willow) cuttings planted in “islands” of 20-30 cuttings in fall 2009 had a three-year survival rate of 82%, while a second set of cuttings planted in fall 2011 had a one-year survival rate of 93%. Visual observations indicate that patches of new vegetation are becoming more predominant on the disturbed area, especially around the willow islands, indicating the importance of microtopography for successful reclamation in arctic environments. Monitoring over ten or more years will be required to determine the long term success of this project.展开更多
文摘Arctic nighttime land-surface temperatures derived by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the NASA Terra and Aqua satellites are investigated. We use the local equator crossing times of 22:30 and 01:30, respectively, in the analysis of changes, trends and variations on the Arctic region and within 120° sectors. We show increases in the number of days above 0°C and significant increase trends over their decadal periods of March 2000 through 2010 (MODIS Terra) and July 2002 through 2012 (MODIS Aqua). The MODIS Aqua nighttime Arctic land-surface temperature change, +0.2°C ± 0.2°C with P-value of 0.01 indicates a reduction relative to the MODIS Terra nighttime Arctic land-surface temperature change, +1.8°C ± 0.3°C with P-value of 0.01. This reduction is a decadal non-stationary component of the Arctic land-surface temperature changes. The reduction is greatest, -1.3°C ± 0.2°C with P-value of 0.01 in the Eastern Russia— Western North American sector of the Arctic during the July 2002 through 2012.
文摘Across the Arctic changes in active layer, melting of glaciers and ground ice, thawing of permafrost and sequestration changes of carbon storage are driven in part by variations of land surface heat absorption, conduction and re-radiation relative to solar irradiance. We investigate Arctic land-surface temperature changes and regional variations derived by the MODIS sensors on NASA Aqua and Terra from March 2000 through July 2012. Over this decadal period we detect increase in the number of days with daytime land-surface temperature above 0℃. There are indications of increasing trends of land-surface temperature change. Regional variations of the changes in land-surface temperature likely arise due to surface material types and topography relative to the daytime variation of solar irradiance.
文摘The diurnal variation of surface temperature is a fundamental parameter as it is a driver of physical processes of atmosphere-land and -ocean energy and mass cycles playing a key role in meteorology and climatology. Our investigation focus is on the diurnal variation of land-surface temperature derived by the Moderate Resolution Imaging Spectroradiometer (MODIS) deployed on the NASA Terra and Aqua satellites. We key our investigation on the ascending and descending mode equator crossing times for daytime and nighttime land-surface temperature variations from March 2000 through 2010 (MODIS-Terra) and July 2002 through 2012 (MODIS-Aqua) and assess the diurnal land-surface temperature range changes at those sampling times. Our investigation shows non-stationary changes in the trends of land-surface temperature diurnal range. We identify changes in the diurnal range trends linked to increase of daytime and nighttime land-surface temperatures from March 2000 through 2010 and decrease in daytime and nighttime land-surface temperatures from July 2002 through 2012. The most recent decrease in daytime and nighttime land-surface temperatures and diurnal range will affect Arctic and other associated energy and mass cycles.
基金This research was supported by the National Natural Science Foundation of China un-der Grant No.40233033.
文摘The influences of the wintertime AO (Arctic Oscillation) on the interdecadal variation of summer monsoon rainfall in East Asia were examined. An interdecadal abrupt change was found by the end of the 1970s in the variation of the AO index and the leading principal component time series of the summer rainfall in East Asia. The rainfall anomaly changed from below normal to above normal in central China, the southern part of northeastern China and the Korean peninsula around 1978. However, the opposite interdecadal variation was found in the rainfall anomaly in North China and South China. The interdecadal variation of summer rainfall is associated with the weakening of the East Asia summer monsoon circulation. It is indicated that the interdecadal variation of the AO exerts an influence on the weakening of the monsoon circulation. The recent trend in the AO toward its high-index polarity during the past two decades plays important roles in the land-sea contrast anomalies and wintertime precipitation anomaly. The mid- and high-latitude regions of the Asian continent are warming, while the low-latitude regions are cooling in winter and spring along with the AO entering its high-index polarity after the late 1970s. In the meantime, the precipitation over the Tibetan Plateau and South China is excessive, implying an increase of soil moisture. The cooling tendency of the land in the southern part of Asia will persist until summer because of the memory of soil moisture. So the warming of the Asian continent is relatively slow in summer. Moreover, the Indian Ocean and Pacific Ocean, which are located southward and eastward of the Asian land, are warming from winter to summer. This suggests that the contrast between the land and sea is decreased in summer. The interdecadal decrease of the land-sea heat contrast finally leads to the weakening of the East Asia summer monsoon circulation.
基金sponsored by the Natural Science Foundation of China (Grant no.41276190)
文摘Using a regional atmospheric model for Arctic climate simulation, two groups of numerical experiments were carried out to study the influence of changes in the underlying surface （land surface, sea surface, and sea ice （LS/SS/SI）） from mild ice years to severe ice years on Arctic climate. In each experiment in the same group, the initial values and lateral boundary conditions were identical. The underlying surface conditions were updated every six hours. The model was integrated for 10 a and monthly mean results were saved for analysis. Variations in annual mean surface air temperature were closely correlated with changes in LS/SS/SI, with a maximum change of more than 15 K. The impact of changes in LS/SS/SI on low-level air temperature was also evident, with significant changes seen over the ocean. However, the maximum change was less than 2 K. For air temperature above 700 hPa, the impact of LS/SS/SI changes was not significant. The distribution of annual mean sea level pressure differences was coincident with the distribution of annual mean sea ice concentration. The difference centers were located in the Barents Sea, the Kara Sea, and the East Siberian Sea, with the maximum value exceeding 3 hPa. For geopotential height, some results passed and some failed a t-test. For results passing the t-test, the area of significance did not decrease with height. There was a significant difference at high levels, with a value of 27 gpm in the difference center at 200 hPa.
文摘Cape Dyer (DYE-M), located on the easternmost point of Baffin Island, is a former DEW line radar station built in 1956-57 which was upgraded in 1993 as part of the current North Warning System. Environmental studies in the late 1990s and early 2000s determined that extensive soil contamination existed across the site, and excavation of six landfills and subsequent reshaping of the area in 2008 disturbed approximately 19,700 m2. A four-year pilot project was conducted between 2009 and 2012 to investigate feasibility of, and determine methods to, accelerate revegetation of the disturbed area through assisted seed dispersal of native and non native species and selective transplantation of slow-growing shrub species. Prior to revegetation efforts, plant surveys conducted in July 2009 determined that 15 species were present in the undisturbed areas, of which Salix arctica (~11%), Vaccinium uliginosum L. (~8%), and Empetrum nigrum L. (~5%) were the predominant species. A total of 14 species (three new) were observed growing on the disturbed areas between 2010 and 2012. The majority of Lolium multiflorum (annual ryegrass) seeds planted as a nurse species in 2009 grew in 2010, but most were stunted and only observed in furrows or sheltered areas at a low density. Salix arctica Pall. (willow) cuttings planted in “islands” of 20-30 cuttings in fall 2009 had a three-year survival rate of 82%, while a second set of cuttings planted in fall 2011 had a one-year survival rate of 93%. Visual observations indicate that patches of new vegetation are becoming more predominant on the disturbed area, especially around the willow islands, indicating the importance of microtopography for successful reclamation in arctic environments. Monitoring over ten or more years will be required to determine the long term success of this project.
