Comparison of the sensitivity of surface downward longwave radiation to changes in water vapor at two high elevation sites

AbstractThe Kanto district, Japan, including Tokyo, has 40 million inhabitants and its summer climate is characterized by high temperature and humidity. The Kuroshio that flows off the southern coast of Kanto district has taken a large meander (LM) path since the summer of 2017 for the first time since the 2004–2005 event. Recently-developed satellite observations detected marked coastal warming off the Kanto-Tokai district during the LM path period. By conducting regional atmospheric model experiments, it is found that summertime coastal warming increases water vapor in the low-level atmosphere through enhanced evaporation from the ocean and influences near-surface winds via the vertical mixing effect over the warming area. These two changes induce an increase in water vapor in Kanto district, leading to an increase in downward longwave radiation at the surface and then surface warming through a local greenhouse effect. Resultantly the summer in Kanto district becomes increasingly hot and humid in LM years, with double the number of discomfort days compared with non-LM years. Our simulations and supplementary observational studies reveal the significant impacts of the LM-induced coastal warming on the summertime climate in Japan, which can exceed previously identified atmospheric teleconnections and climate patterns. Our results could improve weather and seasonal climate forecasts in this region.

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An Improved Parameterization for Retrieving Clear-Sky Downward Longwave Radiation from Satellite Thermal Infrared Data

Remote Sensing ◽

10.3390/rs11040425 ◽

2019 ◽

Vol 11 (4) ◽

pp. 425

Author(s):

Shanshan Yu ◽

Xiaozhou Xin ◽

Qinhuo Liu ◽

Hailong Zhang ◽

Li Li

Keyword(s):

Water Vapor ◽

Simulated Data ◽

Longwave Radiation ◽

Thermal Infrared ◽

Reanalysis Data ◽

Atmospheric Parameter ◽

Near Surface ◽

Modis Data ◽

Clear Sky ◽

Downward Longwave Radiation

Surface downward longwave radiation (DLR) is a crucial component in Earth’s surface energy balance. Yu et al. (2013) developed a parameterization for retrieving clear-sky DLR at high spatial resolution by combined use of satellite thermal infrared (TIR) data and column integrated water vapor (IWV). We extended the Yu2013 parameterization to Moderate Resolution Imaging Spectroradiometer (MODIS) data based on atmospheric radiative simulation, and we modified the parameterization to decrease the systematic negative biases at large IWVs. The new parameterization improved DLR accuracy by 1.9 to 3.1 W/m2 for IWV ≥3 cm compared to the Yu2013 algorithm. We also compared the new parameterization with four algorithms, including two based on Top-of-Atmosphere (TOA) radiance and two using near-surface meteorological parameters and water vapor. The algorithms were first evaluated using simulated data and then applied to MODIS data and validated using surface measurements at 14 stations around the globe. The results suggest that the new parameterization outperforms the TOA-radiance based algorithms in the regions where ground temperature is substantially different (enough that the difference between them is as large as 20 K) from skin air temperature. The parameterization also works well at high elevations where atmospheric parameter-based algorithms often have large biases. Furthermore, comparing different sources of atmospheric input data, we found that using the parameters interpolated from atmospheric reanalysis data improved the DLR estimation by 7.8 W/m2 for the new parameterization and 19.1 W/m2 for other algorithms at high-altitude sites, as compared to MODIS atmospheric products.

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What Drives the North Atlantic Oscillation’s Temperature Anomaly Pattern? Part II: A Decomposition of the Surface Downward Longwave Radiation Anomalies

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0028.1 ◽

2019 ◽

Vol 77 (1) ◽

pp. 199-216 ◽

Cited By ~ 1

Author(s):

Joseph P. Clark ◽

Steven B. Feldstein

Keyword(s):

Water Vapor ◽

Radiative Transfer ◽

Water Flux ◽

Vertical Mixing ◽

Longwave Radiation ◽

Temperature Anomalies ◽

Clear Sky ◽

The North ◽

Downward Longwave Radiation ◽

Thermodynamic Energy

Abstract Radiative transfer calculations are conducted to determine the contribution of temperature and water vapor anomalies toward the surface clear-sky downward longwave radiation (DLR) anomalies of the NAO. These calculations are motivated by the finding that the NAO’s skin temperature anomalies are driven primarily by changes in surface DLR. The clear-sky radiative transfer calculations follow the result that the clear-sky surface DLR anomalies can account for most of the all-sky surface DLR anomalies of the NAO. The results of the radiative transfer calculations prompt an analysis of the thermodynamic energy and total column water (TCW) budget equations, as water vapor and temperature anomalies are found to be equally important drivers of the surface DLR anomalies of the NAO. Composite analysis of the thermodynamic energy equation reveals that the temperature anomalies of the NAO are wind driven: the advection of climatological temperature by the anomalous wind drives the NAO’s temperature anomalies at all levels except for those in the upper troposphere–lower stratosphere where the advection of anomalous temperature by the climatological wind becomes dominant. A similar analysis of the TCW budget reveals that changes in TCW are driven by water flux convergence. In addition to determining the drivers of the temperature and TCW anomalies, the thermodynamic energy and water budget analyses reveal that the decay of the temperature anomalies occurs primarily through vertical mixing, and that of the water anomalies mostly by evaporation minus precipitation.

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Estimation of Long-Term Surface Downward Longwave Radiation over the Global Land from 2000 to 2018

Remote Sensing ◽

10.3390/rs13091848 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1848

Author(s):

Chunjie Feng ◽

Xiaotong Zhang ◽

Yu Wei ◽

Weiyu Zhang ◽

Ning Hou ◽

...

Keyword(s):

Water Vapor ◽

Spatial Resolution ◽

Land Surface ◽

Longwave Radiation ◽

Surface Radiation ◽

Radiation Budget ◽

Mean Bias Error ◽

Downward Longwave Radiation ◽

Global Land

It is of great importance for climate change studies to construct a worldwide, long-term surface downward longwave radiation (Ld, 4–100 μm) dataset. Although a number of global Ld datasets are available, their low accuracies and coarse spatial resolutions limit their applications. This study generated a daily Ld dataset with a 5-km spatial resolution over the global land surface from 2000 to 2018 using atmospheric parameters, which include 2-m air temperature (Ta), relative humidity (RH) at 1000 hPa, total column water vapor (TCWV), surface downward shortwave radiation (Sd), and elevation, based on the gradient boosting regression tree (GBRT) method. The generated Ld dataset was evaluated using ground measurements collected from AmeriFlux, AsiaFlux, baseline surface radiation network (BSRN), surface radiation budget network (SURFRAD), and FLUXNET networks. The validation results showed that the root mean square error (RMSE), mean bias error (MBE), and correlation coefficient (R) values of the generated daily Ld dataset were 17.78 W m−2, 0.99 W m−2, and 0.96 (p < 0.01). Comparisons with other global land surface radiation products indicated that the generated Ld dataset performed better than the clouds and earth’s radiant energy system synoptic (CERES-SYN) edition 4.1 dataset and ERA5 reanalysis product at the selected sites. In addition, the analysis of the spatiotemporal characteristics for the generated Ld dataset showed an increasing trend of 1.8 W m−2 per decade (p < 0.01) from 2003 to 2018, which was closely related to Ta and water vapor pressure. In general, the generated Ld dataset has a higher spatial resolution and accuracy, which can contribute to perfect the existing radiation products.

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Influence of water vapor and aerosols on downward longwave radiation in the high mountain region of Musala peak, Bulgaria

Journal of the Bulgarian Geographical Society ◽

10.3897/jbgs.e73825 ◽

2021 ◽

Vol 44 ◽

pp. 59-72

Author(s):

Peter Nojarov ◽

Todor Arsov ◽

Ivo Kalapov ◽

Hristo Angelov

Keyword(s):

Water Vapor ◽

Air Temperature ◽

Main Tool ◽

Longwave Radiation ◽

Mountain Region ◽

Specific Humidity ◽

High Mountain ◽

Air Temperatures ◽

Downward Longwave Radiation ◽

Influence Of Water

This study reveals the effect of aerosols and water vapor on downward longwave radiation in the high mountain region of Musala peak, Bulgaria. The investigated period is 01/01/2017 (Jan. 1st 2017) – 30/09/2019 (Sep. 30th 2019). Statistical methods are the main tool for discovering the relationships between the different elements. The results indicate that air temperature is the leading factor for downward longwave radiation, specific humidity, and amount of aerosols in the air. That is why, in order to reveal the pure relationship between downward longwave radiation, specific humidity and amount of aerosols in the atmosphere, the air temperature was cleared from the data series. After this procedure, the results show that specific humidity has a significant influence on the downward longwave radiation flux, and an increase of 1% of the specific humidity results in an increase of about 12-15% in the values   of the downward longwave radiation. At air temperatures around 0ºC the influence of water vapor on the downward longwave flux is highest, which is due to the phase transitions of the water – a process during which release/absorption of radiation in the longwave spectrum occurs. The amount of aerosols in the atmosphere also has a significant effect on this type of radiation, and an increase of 1% of the amount of aerosols in the air at air temperatures above –5.5°C results in an increase of the downward longwave radiation of about 2-4%. The findings of this study show that coarser and opaque aerosol particles have a stronger effect on downward longwave radiation. In the area of Musala peak, as the air temperature rises, there is an increase in the amount of aerosols in the air, a decrease in their size, and a transition from transparent to opaque aerosols. The combination of these different tendencies causes the influence of aerosols on downward longwave radiation to be strongest in the middle temperature interval – air temperatures between –5.5°C and +5.5°C. Due to the increased total amount of aerosols and increased amount of opaque aerosols, their influence on downward longwave radiation is significant also at air temperatures above 5.5°C.

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On the Suitability of Current Atmospheric Reanalyses for Regional Warming Studies over China

10.5194/acp-2017-966 ◽

2017 ◽

Cited By ~ 1

Author(s):

Chunlüe Zhou ◽

Yanyi He ◽

Kaicun Wang

Keyword(s):

Regional Climate ◽

Surface Air Temperature ◽

Longwave Radiation ◽

Regional Climate Change ◽

Precipitation Frequency ◽

Regional Warming ◽

Downward Longwave Radiation ◽

In Situ Observations ◽

Mean Differences

Abstract. Reanalyses have been widely used because they add value to the routine observations by generating physically/dynamically consistent and spatiotemporally complete atmospheric fields. Existing studies have extensively discussed their temporal suitability in global change study. This study moves forward on their suitability for regional climate change study where land–atmosphere interactions play a more important role. Here, surface air temperature (Ta) from 12 current reanalysis products were investigated, focusing on spatial patterns of Ta trends, using homogenized Ta from 1979 to 2010 at ~ 2200 meteorological stations in China. Results show that ~ 80 % of the Ta mean differences between reanalyses and in-situ observations are attributed to station and model-grid elevation differences, denoting good skill in Ta climatology and rebutting the previously reported Ta biases. However, the Ta trend biases in reanalyses display spatial divergence (standard deviation = 0.15–0.30 °C/decade at 1° × 1° grids). The simulated Ta trend biases correlate well with those of precipitation frequency, surface incident solar radiation (Rs), and atmospheric downward longwave radiation (Ld) among the reanalyses (r = −0.83, 0.80 and 0.77, p

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An efficient hybrid method for estimating clear-sky surface downward longwave radiation from MODIS data

Journal of Geophysical Research Atmospheres ◽

10.1002/2016jd026250 ◽

2017 ◽

Vol 122 (5) ◽

pp. 2616-2630 ◽

Cited By ~ 14

Author(s):

Jie Cheng ◽

Shunlin Liang ◽

Wenhui Wang ◽

Yamin Guo

Keyword(s):

Hybrid Method ◽

Longwave Radiation ◽

Modis Data ◽

Clear Sky ◽

Downward Longwave Radiation

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Mechanism of Seasonal Arctic Sea Ice Evolution and Arctic Amplification

10.5194/tc-2016-69 ◽

2016 ◽

Author(s):

Kwang-Yul Kim ◽

Benjamin D. Hamlington ◽

Hanna Na ◽

Jinju Kim

Keyword(s):

Heat Flux ◽

Sea Ice ◽

Air Temperature ◽

Surface Air Temperature ◽

Longwave Radiation ◽

The Arctic ◽

Turbulent Heat ◽

Arctic Amplification ◽

Ice Melting ◽

Downward Longwave Radiation

Abstract. Sea ice melting is proposed as a primary reason for the Artic amplification, although physical mechanism of the Arctic amplification and its connection with sea ice melting is still in debate. In the present study, monthly ERA-interim reanalysis data are analyzed via cyclostationary empirical orthogonal function analysis to understand the seasonal mechanism of sea ice melting in the Arctic Ocean and the Arctic amplification. While sea ice melting is widespread over much of the perimeter of the Arctic Ocean in summer, sea ice remains to be thin in winter only in the Barents-Kara Seas. Excessive turbulent heat flux through the sea surface exposed to air due to sea ice melting warms the atmospheric column. Warmer air increases the downward longwave radiation and subsequently surface air temperature, which facilitates sea surface remains to be ice free. A 1 % reduction in sea ice concentration in winter leads to ~ 0.76 W m−2 increase in upward heat flux, ~ 0.07 K increase in 850 hPa air temperature, ~ 0.97 W m−2 increase in downward longwave radiation, and ~ 0.26 K increase in surface air temperature. This positive feedback mechanism is not clearly observed in the Laptev, East Siberian, Chukchi, and Beaufort Seas, since sea ice refreezes in late fall (November) before excessive turbulent heat flux is available for warming the atmospheric column in winter. A detailed seasonal heat budget is presented in order to understand specific differences between the Barents-Kara Seas and Laptev, East Siberian, Chukchi, and Beaufort Seas.

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Tropical cyclone eyewall thunderstorms as a driver of upper tropospheric water vapor increases

10.5194/egusphere-egu21-4269 ◽

2021 ◽

Author(s):

Colin Price ◽

Tair Plotnik ◽

Anirban Guha ◽

Joydeb Saha`

Keyword(s):

Global Warming ◽

Water Vapor ◽

Tropical Cyclones ◽

Longwave Radiation ◽

Maximum Intensity ◽

Lightning Activity ◽

Maximum Enhancement ◽

The Earth ◽

The Future ◽

The Impact

<p>Tropical cyclones have been observed in recent years to be increasing in intensity due to global warming, and projections for the future are for further shifts to stronger tropical cyclones, while the changes in the number of storms is less certain in the future.&#160; These storms have been shown to exhibit strong lightning activity in the eyewall and rainbands, and some studies (Price et al., 2009) showed that the lightning activity peaks before the maximum intensity of the tropical cyclones.&#160; Now we have investigated the impact of these tropical storms on the upper tropospheric water vapor (UTWV) content.&#160; Using the ERA5 reanalysis product from the ECMWF center, together with lightning data from the ENTLN network, we show that the lightning activity in tropical cyclones is closely linked to the increase in UTWV above these storms.&#160; We find the maximum enhancement in UTWV occurs between the 100-300 mb pressure levels, with a lag of 0-2 days after the peak of the storm intensity (measured by the maximum sustained winds in the eyewall).&#160; The lightning activity peaks before the storm reaches its maximum intensity, as found in previous studies.&#160; The interest in UTWV concentrations is due to the strong positive feedback that exists between the amounts of UTWV and surface global warming.&#160; Water Vapor is a strong greenhouse gas which is most efficient in trapping in longwave radiation emitted from the Earth in the upper troposphere.&#160; Small changes in UTWV over time can result in strong surface warming.&#160; If tropical cyclones increase in intensity in the future, this will likely result in increases in UTWV, reducing the natural cooling ability of the Earth.&#160; Lightning may be a useful tool to monitor these changes.</p>

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The Role of Horizontal Temperature Advection on Arctic Amplification

Journal of Climate ◽

10.1175/jcli-d-19-0937.1 ◽

2021 ◽

pp. 1-54

Author(s):

Joseph P. Clark ◽

Vivek Shenoy ◽

Steven B. Feldstein ◽

Sukyoung Lee ◽

Michael Goss

Keyword(s):

Chukchi Sea ◽

Surface Air Temperature ◽

Longwave Radiation ◽

Warming Trend ◽

Surface Energy Budget ◽

Arctic Amplification ◽

Self Organizing Maps ◽

Temperature Advection ◽

Downward Longwave Radiation ◽

Barents And Kara Seas

AbstractThe wintertime (December – February) 1990 - 2016 Arctic surface air temperature (SAT) trend is examined using self-organizing maps (SOMs). The high dimensional SAT dataset is reduced into nine representative SOM patterns, with each pattern exhibiting a decorrelation time scale about 10 days and having about 85% of its variance coming from intraseasonal timescales. The trend in the frequency of occurrence of each SOM pattern is used to estimate the interdecadal Arctic winter warming trend associated with the SOM patterns. It is found that trends in the SOM patterns explain about one-half of the SAT trend in the Barents and Kara Seas, one-third of the SAT trend around Baffin Bay and two-thirds of the SAT trend in the Chukchi Sea. A composite calculation of each term in the thermodynamic energy equation for each SOM pattern shows that the SAT anomalies grow primarily through the advection of the climatological temperature by the anomalous wind. This implies that a substantial fraction of Arctic amplification is due to horizontal temperature advection that is driven by changes in the atmospheric circulation. An analysis of the surface energy budget indicates that the skin temperature anomalies as well as the trend, although very similar to that of the SAT, are produced primarily by downward longwave radiation.

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