Characteristics of Turbulence and Aerosol Optical and Radiative Properties during Haze–Fog Episodes in Shenyang, Northeast China

The characteristics of turbulence in the planetary boundary layer (PBL) and the aerosol optical and radiative properties during haze and haze–fog mixed episodes on 22–27 January 2021, in Shenyang, a provincial city in Northeast China, were analyzed using meteorological and aerosol observations. During the haze episode, the hourly mean PM2.5 concentration reached a maximum of 337 µg m−3 and visibility decreased to 1.6 km. The PM2.5 concentration decreased gradually during the haze–fog mixed episode as a result of the scavenging effects of fog, but visibility mostly remained below 1 km owing to high ambient relative humidity (>90%). During the haze–fog mixed episode, an increasing proportion of PM2.5 led to a higher ratio of the backward to the total scattering coefficient. As fog occurred, downward shortwave radiation arriving at the surface was significantly reduced, and upward longwave radiation increased and almost equaled the downward longwave radiation, which can be used as a good indicator for distinguishing haze and fog. Mechanical turbulence was weak during both episodes, and latent heat flux varied within a wider range during the haze–fog mixed episode. The PBL dynamic structure affected the vertical distribution of aerosols/fog droplets. Aerosol-rich layers appeared at altitudes below 0.5 km and above 0.6 km during the haze episode. The elevated aerosol layer was related to the aerosol transport from upstream polluted areas caused by strong upper-level turbulence, and it began to mix vertically after sunrise because of convective turbulence. Aerosols and fog droplets were mostly trapped in a shallower PBL with a height of 0.2–0.4 km during the haze–fog mixed episode because of weaker turbulence.

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Trends in surface radiation and cloud radiative effect at four Swiss sites for the 1996–2015 period

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-13227-2019 ◽

2019 ◽

Vol 19 (20) ◽

pp. 13227-13241 ◽

Cited By ~ 3

Author(s):

Stephan Nyeki ◽

Stefan Wacker ◽

Christine Aebi ◽

Julian Gröbner ◽

Giovanni Martucci ◽

...

Keyword(s):

Longwave Radiation ◽

Ground Temperature ◽

Surface Radiation ◽

Specific Humidity ◽

Shortwave Radiation ◽

Radiative Effect ◽

Cloud Properties ◽

Cloud Radiative Effect ◽

Downward Longwave Radiation ◽

Integrated Water Vapour

Abstract. The trends of meteorological parameters and surface downward shortwave radiation (DSR) and downward longwave radiation (DLR) were analysed at four stations (between 370 and 3580 m a.s.l.) in Switzerland for the 1996–2015 period. Ground temperature, specific humidity, and atmospheric integrated water vapour (IWV) trends were positive during all-sky and cloud-free conditions. All-sky DSR and DLR trends were in the ranges of 0.6–4.3 W m−2 decade−1 and 0.9–4.3 W m−2 decade−1, respectively, while corresponding cloud-free trends were −2.9–3.3 W m−2 decade−1 and 2.9–5.4 W m−2 decade−1. Most trends were significant at the 90 % and 95 % confidence levels. The cloud radiative effect (CRE) was determined using radiative-transfer calculations for cloud-free DSR and an empirical scheme for cloud-free DLR. The CRE decreased in magnitude by 0.9–3.1 W m−2 decade−1 (only one trend significant at 90 % confidence level), which implies a change in macrophysical and/or microphysical cloud properties. Between 10 % and 70 % of the increase in DLR is explained by factors other than ground temperature and IWV. A more detailed, long-term quantification of cloud changes is crucial and will be possible in the future, as cloud cameras have been measuring reliably at two of the four stations since 2013.

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Analysis of the Radiation Fluxes over Complex Surfaces on the Tibetan Plateau

Water ◽

10.3390/w13213084 ◽

2021 ◽

Vol 13 (21) ◽

pp. 3084

Author(s):

Chunxiao Wang ◽

Yaoming Ma ◽

Binbin Wang ◽

Weiqiang Ma ◽

Xuelong Chen ◽

...

Keyword(s):

Tibetan Plateau ◽

Surface Temperature ◽

Air Temperature ◽

Surface Albedo ◽

Longwave Radiation ◽

Heat Fluxes ◽

Shortwave Radiation ◽

The Tibetan Plateau ◽

Downward Shortwave Radiation ◽

Downward Longwave Radiation

Analysis of long-term, ground-based observation data on the Tibetan Plateau help to enhance our understanding of land-atmosphere interactions and their influence on weather and climate in this region. In this paper, the daily, monthly, and annual averages of radiative fluxes, surface albedo, surface temperature, and air temperature were calculated for the period of 2006 to 2019 at six research stations on the Tibetan Plateau. The surface energy balance characteristics of these six stations, which include alpine meadow, alpine desert, and alpine steppe, were then compared. The downward shortwave radiation at stations BJ, QOMS, and NAMORS was found to decrease during the study period, due to increasing cloudiness. Meanwhile, the upward shortwave radiation and surface albedo at all stations were found to have decreased overall. Downward longwave radiation, upward longwave radiation, net radiation, surface temperature, and air temperature showed increasing trends on inter-annual time scales at most stations. Downward shortwave radiation was maximum in spring at BJ, QOMS, NADORS, and NAMORS, due to the influence of the summer monsoon. Upward shortwave radiation peaked in October and November due to the greater snow cover. BJ, QOMS, NADORS, and NAMORS showed strong sensible heat fluxes in the spring while MAWORS showed strong sensible heat fluxes in the summer. The monthly and diurnal variations of surface albedo at each station were “U” shaped. The diurnal variability of downward longwave radiation at each station was small, ranging from 220 to 295 W·m−2.The diurnal variation in surface temperature at each station slightly lagged behind changes in downward shortwave radiation, and the air temperature, in turn, slightly lagged behind the surface temperature.

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Revising short and longwave radiation archives in view of possible revisions of the WSG and WISG reference scales: Methods and implications

10.5194/amt-2017-41 ◽

2017 ◽

Author(s):

Stephan Nyeki ◽

Stefan Wacker ◽

Julian Gröbner ◽

Wolfgang Finsterle ◽

Martin Wild

Keyword(s):

Time Series ◽

Longwave Radiation ◽

Surface Radiation ◽

Shortwave Radiation ◽

Standard Group ◽

Water Vapour Content ◽

Data Archives ◽

Downward Longwave Radiation ◽

Integrated Water Vapour ◽

A Minor

Abstract. A large number of radiometers are traceable to the World Standard Group (WSG) for shortwave radiation and the interim World Infra-red Standard Group (WISG) for longwave radiation, hosted by the Physikalisch Meteorologisches Observatorium Davos/World Radiation Centre (PMOD/WRC, Davos, Switzerland). The WSG and WISG have recently been found to over- and underestimate radiation values, respectively (Fehlmann et al., 2012; Gröbner et al., 2014), although research is still ongoing. In view of a possible revision of the reference scales of both standard groups, this study discusses the methods involved, and the implications on existing archives of radiation time-series, such as the Baseline Surface Radiation Network (BSRN). Based on PMOD/WRC calibration archives and BSRN data archives, the downward longwave radiation (DLR) time-series over the 2006–2015 periods were analysed at four stations (polar and mid-latitude locations). DLR was found to increase by up to 3.5 and 5.4 W m−2, respectively, after applying a WISG reference scale correction and a minor correction for the dependence of pyrgeometer sensitivity on atmospheric integrated water vapour content. Similar increases in DLR may be expected at other BSRN stations. Based on our analysis, a number of recommendations are made for future studies.

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Revising shortwave and longwave radiation archives in view of possible revisions of the WSG and WISG reference scales: methods and implications

Atmospheric Measurement Techniques ◽

10.5194/amt-10-3057-2017 ◽

2017 ◽

Vol 10 (8) ◽

pp. 3057-3071 ◽

Cited By ~ 6

Author(s):

Stephan Nyeki ◽

Stefan Wacker ◽

Julian Gröbner ◽

Wolfgang Finsterle ◽

Martin Wild

Keyword(s):

Time Series ◽

Longwave Radiation ◽

Surface Radiation ◽

Shortwave Radiation ◽

Standard Group ◽

Water Vapour Content ◽

Data Archives ◽

Downward Longwave Radiation ◽

Integrated Water Vapour ◽

A Minor

Abstract. A large number of radiometers are traceable to the World Standard Group (WSG) for shortwave radiation and the interim World Infrared Standard Group (WISG) for longwave radiation, hosted by the Physikalisch-Meteorologisches Observatorium Davos/World Radiation Centre (PMOD/WRC, Davos, Switzerland). The WSG and WISG have recently been found to over- and underestimate radiation values, respectively (Fehlmann et al., 2012; Gröbner et al., 2014), although research is still ongoing. In view of a possible revision of the reference scales of both standard groups, this study discusses the methods involved and the implications on existing archives of radiation time series, such as the Baseline Surface Radiation Network (BSRN). Based on PMOD/WRC calibration archives and BSRN data archives, the downward longwave radiation (DLR) time series over the 2006–2015 period were analysed at four stations (polar and mid-latitude locations). DLR was found to increase by up to 3.5 and 5.4 W m−2 for all-sky and clear-sky conditions, respectively, after applying a WISG reference scale correction and a minor correction for the dependence of pyrgeometer sensitivity on atmospheric integrated water vapour content. Similar increases in DLR may be expected at other BSRN stations. Based on our analysis, a number of recommendations are made for future studies.

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Urban Energy Balance Obtained from the Comprehensive Outdoor Scale Model Experiment. Part II: Comparisons with Field Data Using an Improved Energy Partition

Journal of Applied Meteorology and Climatology ◽

10.1175/2010jamc1993.1 ◽

2010 ◽

Vol 49 (7) ◽

pp. 1360-1376 ◽

Cited By ~ 15

Author(s):

Toru Kawai ◽

Manabu Kanda

Keyword(s):

Energy Balance ◽

Seasonal Variations ◽

Heat Storage ◽

Longwave Radiation ◽

Energy Partitioning ◽

Urban Canyon ◽

Shortwave Radiation ◽

Scale Model ◽

Urban Energy Balance ◽

Downward Longwave Radiation

Abstract The objective of this study is to examine the differences and similarities in the annual trends of the urban surface energy balance (SEB) among long-term field measurements. Four datasets analyzed for the study were collected in the following experiments or observational sites: Comprehensive Outdoor Scale Model experiments (COSMO), the Kugahara site in Tokyo, Japan (Ku04), and the Sperrstrasse and Spalenring sites in Basel, Switzerland (BuU1 and BuU2). A new variable, the forcing radiation QFR, has been proposed to replace the conventional net radiation Q* for the normalization of the SEB components. Here, QFR is defined as the sum of net shortwave radiation and downward longwave radiation. Because QFR does not include the upward longwave radiation, it is independent of the surface temperature, which is determined by the energy partitioning process. Therefore, QFR is independent of the energy partitioning process itself. With the use of QFR, the characteristics of the daytime normalized components of the SEB equation (i.e., upward longwave radiation, QL↑/QFR, turbulence fluxes (QH + QE)/QFR, and heat storage ΔQS/QFR) were investigated. The above energy fluxes normalized by the forcing radiation depended on the friction velocity u*. An increase of u* predominantly enhanced (QH + QE)/QFR and reduced both QL↑/QFR and ΔQS/QFR. When this u* dependency on the SEB was taken into consideration, the annual variations of these three flux ratios from cities located in similar latitudes and longitudes (i.e., BuU1 and BuU2, Ku04, and COSMO) were very similar. At BuU1 and BuU2, QL↑/QFR showed larger seasonal amplitudes than at COSMO and Ku04. The seasonal variations of (QH + QE)/QFR were roughly out of phase with respect to those of QL↑/QFR, resulting in relatively small seasonal variations of ΔQS/QFR. Furthermore, the effects of urban canyon geometry on the SEB were examined by comparing the SEB for the roofs to that for the canyon. The three-dimensional urban canyon geometry enhanced the heat storage efficiency relative to the forcing radiation ΔQS/QFR of the canyon in comparison with that of roofs or flat surfaces. This observation was explained by the continuous movement of sunlit areas on the walls and streets.

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Longwave atmospheric radiation over Antarctica

Antarctic Science ◽

10.1017/s0954102096000132 ◽

1996 ◽

Vol 8 (1) ◽

pp. 105-109 ◽

Cited By ~ 13

Author(s):

J.C. King

Keyword(s):

General Circulation ◽

Inversion Layer ◽

Circulation Model ◽

Longwave Radiation ◽

Radiative Properties ◽

Fourth Power ◽

Surface Inversion ◽

Downward Longwave Radiation ◽

Using Data ◽

The Antarctic

The seasonal and spatial variation of downward longwave radiation (L↓) at the surface of the Antarctic ice sheet is studied using data from four stations. L↓ is found to depend on the fourth power of the surface temperature but on the sixth power of the temperature at the top of the surface inversion layer. The former result is shown to be a consequence of the dominance of longwave radiation in the surface energy balance while the latter raises some questions concerning the radiative properties of Antarctic clouds. Simple parametrizations of L↓ as a function of temperature are suggested; these may find application in validating General Circulation Model radiation calculations over Antarctica.

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Projected near-term changes in three types of heat waves over China under RCP4.5

10.5194/egusphere-egu2020-12349 ◽

2020 ◽

Author(s):

Qin Su

Keyword(s):

Climate Models ◽

Heat Waves ◽

Longwave Radiation ◽

Ocean Model ◽

Shortwave Radiation ◽

Minor Role ◽

Air Temperatures ◽

Downward Longwave Radiation ◽

Near Term ◽

Projected Changes

The changes in three aspects of frequency, intensity and duration of the compound, daytime and nighttime heat waves (HWs) over China during extended summer (May&#8211;September) in a future period of the mid-21st century (FP; 2045-2055) under RCP4.5 scenario relative to present day (PD; 1994-2011) are investigated by two models, MetUM-GOML1 and MetUM-GOML2, which comprise the atmospheric components of two state-of-the-art climate models coupled to a multi-level mixed-layer ocean model. The results show that in the mid-21st century all three types of HWs in China will occur more frequently with strengthened intensity and elongated duration relative to the PD. The compound HWs will change most dramatically, with the frequency in the FP being 4&#8211;5 times that in the PD, and the intensity and duration doubling those in the PD. The changes in daytime and nighttime HWs are also remarkable, with the changes of nighttime HWs larger than those of daytime HWs. The future changes of the three types of HWs in China in two models are similar in terms of spatial patterns and area-averaged quantities, indicating these projected changes of HWs over the China under RCP4.5 scenario are robust. Further analyses suggest that projected future changes in HWs over China are determined mainly by the increase in seasonal mean surface air temperatures with change in temperature variability playing a minor role. The seasonal mean temperature increase is due to the increase in surface downward longwave radiation and surface shortwave radiation. The increase in downward longwave radiation results from the enhanced greenhouse effect and increased water vapour in the atmosphere. The increase in surface shortwave radiation is the result of the decreased aerosol emissions, via direct aerosol-radiation interaction and indirect aerosol-cloud interaction over southeastern and northeastern China, and the reduced cloud cover related to a decrease in relative humidity.

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Convection-Aerosol Interactions in the United Arab Emirates: A Sensitivity Study

10.5194/acp-2021-597 ◽

2021 ◽

Author(s):

Ricardo Fonseca ◽

Diana Francis ◽

Michael Weston ◽

Narendra Nelli ◽

Sufian Farah ◽

...

Keyword(s):

United Arab Emirates ◽

Radiation Flux ◽

Positive Impact ◽

Longwave Radiation ◽

Shortwave Radiation ◽

Onset Of Convection ◽

Carbonaceous Particles ◽

Low Level ◽

Aerosol Loading ◽

Downward Longwave Radiation

Abstract. The Weather Research and Forecasting (WRF) model is used to investigate convection-aerosol interactions in the United Arab Emirates for a summertime convective event. Both an idealised and scaled versions of a 7-year climatological aerosol distribution are considered. The convection on 14 August 2013 was triggered by the low-level convergence of the circulation associated with the Arabian Heat Low (AHL) and the daytime sea-breeze circulation. The cold pools associated with the convective events, as well as the low-level wind convergence along the Intertropical Discontinuity (ITD) earlier in the day, explain the dustier environment, with Aerosol Optical Depths (AODs) in excess of two. Due to a colder surface and air temperature, the AHL is incorrectly represented in WRF, which leads to a mismatch between the observed and modelled clouds and precipitation. Employing interior nudging in the outermost grids of the three-nested simulation has a small but positive impact on the model predictions of the innermost nest. This is because the higher temperatures from more accurate boundary conditions are offset by colder temperatures from locally enhanced precipitation, the latter arising from a shift in the position of the AHL. Numerical experiments revealed a high sensitivity to the aerosol properties. In particular, replacing 20 % of the rural aerosols by carbonaceous particles has an impact on the surface radiative fluxes comparable to increasing the aerosol loading by a factor of 10, with a daily-averaged reduction in the UAE-averaged net shortwave radiation flux of ~90 W m−2 and an increase in the net longwave radiation flux of ~51 W m−2. However, in the former, WRF generates 20 % more precipitation than in the latter, due to a broader and weaker AHL. The surface downward and upward shortwave and upward longwave radiation fluxes are found to scale linearly with the aerosol loading, while the downward longwave radiation flux varies by less than ±12 W m−2 when the aerosol amount and/or properties are changed. An increase in the aerosol loading also leads to drier conditions due to a shift in the position of the AHL and rainfall occurring in a drier region, with a domain-wise decrease in the daily accumulated rainfall of 16 % when the aerosol loading is increased by a factor of 10. In addition, the onset of convection is also delayed.

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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 Evaluation of Surface Atmospheric Changes over the Arctic Ocean for 2000–09 Using Recent Reanalyses

Earth Interactions ◽

10.1175/ei-d-14-0012.1 ◽

2015 ◽

Vol 19 (2) ◽

pp. 1-18 ◽

Cited By ~ 1

Author(s):

Ayan H. Chaudhuri ◽

Rui M. Ponte

Keyword(s):

Arctic Ocean ◽

Extreme Event ◽

Longwave Radiation ◽

Remotely Sensed ◽

Surface Radiation ◽

Shortwave Radiation ◽

The Arctic ◽

Near Surface ◽

The Arctic Ocean ◽

Ice Retreat

Abstract The authors examine five recent reanalysis products [NCEP Climate Forecast System Reanalysis (CFSR), Modern-Era Retrospective Analysis for Research and Applications (MERRA), Japanese 25-year Reanalysis Project (JRA-25), Interim ECMWF Re-Analysis (ERA-Interim), and Arctic System Reanalysis (ASR)] for 1) trends in near-surface radiation fluxes, air temperature, and humidity, which are important indicators of changes within the Arctic Ocean and also influence sea ice and ocean conditions, and 2) fidelity of these atmospheric fields and effects for an extreme event: namely, the 2007 ice retreat. An analysis of trends over the Arctic for the past decade (2000–09) shows that reanalysis solutions have large spreads, particularly for downwelling shortwave radiation. In many cases, the differences in significant trends between the five reanalysis products are comparable to the estimated trend within a particular product. These discrepancies make it difficult to establish a consensus on likely changes occurring in the Arctic solely based on results from reanalyses fields. Regarding the 2007 ice retreat event, comparisons with remotely sensed estimates of downwelling radiation observations against these reanalysis products present an ambiguity. Remotely sensed observations from a study cited herewith suggest a large increase in downwelling summertime shortwave radiation and decrease in downwelling summertime longwave radiation from 2006 and 2007. On the contrary, the reanalysis products show only small gains in summertime shortwave radiation, if any; however, all the products show increases in downwelling longwave radiation. Thus, agreement within reanalysis fields needs to be further checked against observations to assess possible biases common to all products.

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