scholarly journals An Investigation on Seasonal and Diurnal Cycles of TOA Shortwave Radiations from DSCOVR/EPIC, CERES, MERRA-2, and ERA5

2021 ◽  
Vol 13 (22) ◽  
pp. 4595
Author(s):  
Young-Kwon Lim ◽  
Dong L. Wu ◽  
Kyu-Myong Kim ◽  
Jae N. Lee
Keyword(s):  
Water Content ◽  
Diurnal Cycle ◽  
Liquid Water ◽  
Radiant Energy ◽  
Energy System ◽  
Liquid Water Content ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Western Coast ◽  
Diurnal Variability

Reflected shortwave (SW) solar radiations at the top of atmosphere from Clouds and the Earth’s Radiant Energy System (CERES), Modern Era-Retrospective analysis for Research and Applications version 2 (MERRA-2), and ECMWF Reanalysis 5th Generation (ERA5) are examined to better understand their differences in spatial and temporal variations (seasonal and diurnal cycle timescale) with respect to the observations from the Earth Polychromatic Imaging Camera (EPIC) on the Deep Space Climate Observatory (DSCOVR) satellite. Comparisons between two reanalyses (MERRA-2 and ERA5) and EPIC reveal that MERRA-2 has a generally larger deviation from EPIC than ERA5 in terms of the SW radiance and diurnal variability in all seasons, which can be attributed to larger cloud biases in MERRA-2. MERRA-2 produces more ice/liquid water content than ERA5 over the tropical warm pool, leading to positive SW biases in cloud and radiance, while both reanalyses underestimate the observed SW radiance from EPIC in the stratus-topped region off the western coast of US/Mexico in the boreal summer. Himalaya/Tibet region in the boreal spring/summer and the midlatitude Southern Hemisphere in the boreal winter are the regions where MERRA-2 and ERA5 deviate largely from EPIC, but their deviations have the opposite sign. Vertical structures of cloud ice/liquid water content explain reasonably well these contrasting differences between the two reanalyses. As two independent observations, CERES and EPIC agree well with each other in terms of the SW radiance maps, showing 2–3% mean absolute errors over the tropical midlatitudes. The CERES-EPIC consistency further confirms that the reanalyses still have challenges in representing the SW flux and its global distribution. In the CERES-EPIC observation differences, CERES slightly overestimates the diurnal cycle (as a function of local solar time) of the observed EPIC irradiance in the morning and underestimates it in the afternoon, while the opposite is the case in the reanalyses.

scholarly journals Aerosol liquid water content in the moist southern West African monsoon layer and its radiative impact

2018 ◽  
Author(s):  
Konrad Deetz ◽  
Heike Vogel ◽  
Sophie Haslett ◽  
Peter Knippertz ◽  
Hugh Coe ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Water Content ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Diurnal Cycle ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Scale Model ◽  
Model Framework ◽  
The Impact

Abstract. Water uptake can significantly increase the size and therefore the optical properties of aerosols. In this study, the regional-scale model framework COSMO-ART is applied to Southern West Africa (SWA) for a summer monsoon process study on 2–3 and 6–7 July 2016. The high moisture and aerosol burden in the monsoon layer makes SWA favorable to quantify properties that determine the aerosol liquid water content and its impact on radiative transfer. Given the marked diurnal cycle in SWA, the analysis is separated into three characteristic phases: (a) Atlantic Inflow progression phase (15–2 UTC), when winds from the Gulf of Guinea accelerate in the less turbulent evening and nighttime boundary layer, (b) Moist morning phase (3–8 UTC), when the passage of the Atlantic Inflow front leads to overall cool and moist conditions over land and (c) Daytime drying phase (9–15 UTC), in which the Atlantic Inflow front re-establishes with the inland heating initiated after sunrise. This diurnal cycle imprints, via the relative humidity, also the aerosol liquid water content. We analyzed the impact of relative humidity and clouds on the aerosol liquid water content. As shown by other studies, the accumulation mode particles are the dominant contributor of aerosol liquid water. We find aerosol growth factors of 2 (4) for submicron (coarse) mode particles, leading to a substantial increase of mean aerosol optical depth from 0.2 to 0.7. Considering the aerosol liquid water content leads to a decrease in shortwave radiation of about 20 W m−2, while longwave effects appear to be insignificant, especially during nighttime. The estimated relationships between total column aerosol liquid water and radiation are −305 ± 39 W g−1 (shortwave in-cloud), −114 ± 42 W g−1 (shortwave off-cloud) and about −10 W g−1 (longwave). The results highlight the need to consider the relative humidity dependency of aerosol optical depth in atmospheric models, particularly in moist tropical environments, where their effect on radiation can be very large.

scholarly journals Variability of Regional TOA Flux Diurnal Cycle Composites at the Monthly Time Scale

2014 ◽  
Vol 71 (9) ◽  
pp. 3484-3498 ◽  
Author(s):  
Patrick C. Taylor
Keyword(s):  
North Africa ◽  
Diurnal Cycle ◽  
Shape Change ◽  
Radiant Energy ◽  
Energy System ◽  
Diurnal Variability ◽  
Thermodynamic State ◽  
Temperature And Precipitation ◽  
Cycle Shape ◽  
Atmospheric Dynamic

Abstract Diurnal variability is a fundamental component of Earth’s climate system. Clouds, temperature, and precipitation exhibit robust responses to the daily cycle of solar insolation. Recent work indicates significant variability in the top-of-the-atmosphere (TOA) flux diurnal cycle in the tropics associated with monthly changes in the cloud diurnal cycle evolution. It has been proposed that the observed month-to-month variations in the TOA flux diurnal cycle are caused by anomalies in the atmospheric dynamic and thermodynamic state. This hypothesis is tested using a regression analysis to quantify the relationship between diurnal cycle shape and the atmospheric dynamic and thermodynamic state. TOA radiative fluxes are obtained from Clouds and the Earth’s Radiant Energy System (CERES) Edition 3 data and the atmospheric dynamic and thermodynamic state is taken from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis. Four regions representing traditional diurnal cycle regimes are used in this analysis: North Africa (land nonconvective), central South America (land convective), Peru marine stratocumulus (ocean nonconvective), and Indian Ocean (ocean convective). The results show a statistically significant diurnal cycle shape change and cloud response related to monthly atmospheric state anomalies. Using the single-variable regression relationships to predict monthly diurnal cycle variability shows improvements of 1%–18% over assuming a climatological diurnal cycle shape; the most significant gains are found in North Africa. The proposed hypothesis, therefore, contributes to diurnal cycle variability explaining at least 10%–20% of the total monthly-mean diurnal cycle variability.

scholarly journals Aerosol liquid water content in the moist southern West African monsoon layer and its radiative impact

2018 ◽  
Vol 18 (19) ◽  
pp. 14271-14295 ◽  
Author(s):  
Konrad Deetz ◽  
Heike Vogel ◽  
Sophie Haslett ◽  
Peter Knippertz ◽  
Hugh Coe ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Water Content ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Diurnal Cycle ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Scale Model ◽  
Model Framework ◽  
The Impact

Abstract. Water uptake can significantly increase the size and therefore alters the optical properties of aerosols. In this study, the regional-scale model framework COSMO-ART is applied to southern West Africa (SWA) for a summer monsoon process study on 2–3 and 6–7 July 2016. The high moisture and aerosol burden in the monsoon layer makes SWA favorable to quantify properties that determine the aerosol liquid water content and its impact on radiative transfer. Given the marked diurnal cycle in SWA, the analysis is separated into three characteristic phases: (a) the Atlantic inflow progression phase (15:00–02:00 UTC), when winds from the Gulf of Guinea accelerate in the less turbulent evening and nighttime boundary layer, (b) the moist morning phase (03:00–08:00 UTC), when the passage of the Atlantic inflow front leads to overall cool and moist conditions over land, and (c) the daytime drying phase (09:00–15:00 UTC), in which the Atlantic inflow front reestablishes with the inland heating initiated after sunrise. This diurnal cycle also impacts, via relative humidity, the aerosol liquid water content. We analyzed the impact of relative humidity and clouds on the aerosol liquid water content. As shown by other studies, accumulation-mode particles are the dominant contributor of aerosol liquid water. We find aerosol growth factors of 2 (4) for submicron (coarse-mode) particles, leading to a substantial increase in mean aerosol optical depth from 0.2 to 0.7. Considering the aerosol liquid water content leads to a decrease in shortwave radiation of about 20 W m−2, while longwave effects appear to be insignificant, especially during nighttime. The estimated relationships between total column aerosol liquid water and radiation are -305±39 W g−1 (shortwave in-cloud), -114±42 W g−1 (shortwave off-cloud) and about −10 W g−1 (longwave). The results highlight the need to consider the relative humidity dependency of aerosol optical depth in atmospheric models, particularly in moist tropical environments where their effect on radiation can be very large.

scholarly journals Proof of Concept: Development of Snow Liquid Water Content Profiler Using CS650 Reflectometers at Caribou, ME, USA

Sensors ◽  
2017 ◽  
Vol 17 (3) ◽  
pp. 647 ◽  
Author(s):  
Carlos Pérez Díaz ◽  
Jonathan Muñoz ◽  
Tarendra Lakhankar ◽  
Reza Khanbilvardi ◽  
Peter Romanov
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Concept Development ◽  
Proof Of Concept

Field Measurement of the Liquid-Water Content of Snow

1981 ◽  
Vol 27 (95) ◽  
pp. 175-178 ◽  
Author(s):  
E. M. Morris
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Field Measurement ◽  
Solution Method ◽  
Liquid Water Content ◽  
Field Trials

Abstract Field trials show that the liquid-water content of snow can be determined simply and cheaply by a version of Bader’s solution method.

scholarly journals Snow dielectric properties: from DC to microwave X-band

1994 ◽  
Vol 19 ◽  
pp. 92-96 ◽  
Author(s):  
TH. Achammer ◽  
A. Denoth
Keyword(s):  
Grain Size ◽  
Dielectric Properties ◽  
Water Content ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Frequency Range ◽  
Snow Density ◽  
Cold Room ◽  
X Band ◽  
Grain Size And Shape

Broadband measurements of dielectric properties of natural snow samples near or at 0°C are reported. Measurement quantities are: dielectric permittivity, loss factor and complex propagation factor for electromagnetic waves. X-band measurements were made in a cold room in the laboratory; measurements at low and intermediate frequencies were carried out both in the field (Stubai Alps, 3300 m; Hafelekar near Innsbruck, 2100 m) and in the cold room. Results show that in the different frequency ranges the relative effect on snow dielectric properties of the parameters: density, grain-size and shape, liquid water content, shape and distribution of liquid inclusions and content of impurities, varies significantly. In the low-frequency range the influence of grain-size and shape and snow density dominates; in the medium-frequency range liquid water content and density are the dominant parameters. In the microwave X-band the influence of the amount, shape and distribution of liquid inclusions and snow density is more important than that of the remaining parameters.

Comparison of Water Thickness Profiles of Compressed PEMFC GDLs

2011 ◽  
Author(s):  
Pradyumna Challa ◽  
James Hinebaugh ◽  
A. Bazylak
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Water Distribution ◽  
Polymer Electrolyte Membrane ◽  
Water Injection ◽  
Liquid Water Content ◽  
Gas Diffusion ◽  
Injection Rate ◽  
Water Levels ◽  
Ex Situ

In this paper, through-plane liquid water distribution is analyzed for two polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layers (GDLs). The experiments were conducted in an ex situ flow field apparatus with 1 mm square channels at two distinct flow rates to mimic water production rates of 0.2 and 1.5 A/cm2 in a PEMFC. Synchrotron radiography, which involves high intensity monochromatic X-ray beams, was used to obtain images with a spatial and temporal resolution of 20–25 μm and 0.9 s, respectively. Freudenberg H2315 I6 exhibited significantly higher amounts of water than Toray TGP-H-090 at the instance of breakthrough, where breakthrough describes the event in which liquid water reaches the flow fields. While Freudenberg H2315 I6 exhibited a significant overall decrease in liquid water content throughout the GDL shortly after breakthrough, Toray TGP-H-090 appeared to retain breakthrough water-levels post-breakthrough. It was also observed that the amount of liquid water content in Toray TGP-H-090 (10%.wt PTFE) decreased significantly when the liquid water injection rate increased from 1 μL/min to 8 μL/min.

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