Diurnal and Seasonal Cycles of Cloud Occurrences, Types, and Radiative Impact over West Africa

Bouniol, Dominique; Couvreux, Fleur; Kamsu-Tamo, Pierre Honore; Leplay, Madeleine; Guichard, Françoise; Favot, Florence; O’Connor, Ewan

doi:10.1175/jamc-d-11-051.1

Cited by 58 publications

(78 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Apart from the peak in rainfall at 1500 h (1 mm h −1 ), which may reflect the one‐year sample size, the rainfall is negligible from 0900 h until midnight. A nocturnal preference for rainfall from midnight until 0700 h is consistent with the results of Rickenbach et al () and Bouniol et al (). Many days in the wet season did not experience precipitation while there were some with extremely high rainfall rates, particularly in the afternoon hours, leading to a large standard deviation.…”

Section: Resultssupporting

confidence: 91%

A one‐year study of the diurnal cycle of meteorology, clouds and radiation in the West African Sahel region

Collow

Ghate

Miller

et al. 2015

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

The diurnal cycles of meteorological and radiation variables are analysed during the wet and dry seasons over the Sahel region of West Africa during 2006 using surface data collected by the Atmospheric Radiation Measurement (ARM) programme's Mobile Facility, satellite radiation measurements from the Geostationary Earth Radiation Budget (GERB) instrument aboard Meteosat 8, and reanalysis products from the National Centers for Environmental Prediction (NCEP). The meteorological analysis builds upon past studies of the diurnal cycle in the region by incorporating diurnal cycles of lower tropospheric wind profiles, thermodynamic profiles, integrated water vapour and liquid water measurements, and cloud radar measurements of frequency and location. These meteorological measurements are complemented by 3 h measurements of the diurnal cycles of the top‐of‐atmosphere (TOA) and surface short‐wave (SW) and long‐wave (LW) radiative fluxes and cloud radiative effects (CREs), and the atmospheric radiative flux divergence (RFD) and atmospheric CREs. Cirrus cloudiness during the dry season is shown to peak in coverage in the afternoon, while convective clouds during the wet season are shown to peak near dawn and have an afternoon minimum related to the rise of the lifting condensation level into the Saharan Air Layer. The LW and SW RFDs and CREs exhibit diurnal cycles during both seasons, but there is a relatively small difference in the LW cycles during the two seasons (10 − 30 W m−2 depending on the variable and time of day). Small differences in the TOA CREs during the two seasons are overwhelmed by large differences in the surface SW CREs, which exceed 100 W m−2. A significant surface SW CRE during the wet season combined with a negligible TOA SW CRE produces a diurnal cycle in the atmospheric CRE that is modulated primarily by the SW surface CRE, peaks at midday at ∼150 W m−2, and varies widely from day to day.

show abstract

Section: Resultssupporting

confidence: 91%

A one‐year study of the diurnal cycle of meteorology, clouds and radiation in the West African Sahel region

Collow

Ghate

Miller

et al. 2015

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

show abstract

“…During DJF and MAM, CERES does not show a well‐marked spatial variability of LCC between the Guinean (south) and Sahel/Sahara (north) regions. Surprisingly, CERES shows LCC over the Sahel/Sahara areas (up to about 20%) during the entire year, considering that low clouds (example shallow convective systems) rarely occur over these areas except in the core of the monsoon season (Bouniol et al ., ). A spatial gradient of low‐level convection between the Sahelian and Guinean regions is thus expected due to the proximity of the latter to the ocean, leading to an influx of moisture from oceanic breezes and thus enhancing convection over these regions.…”

Section: Cloud Cover Variability In Wamentioning

confidence: 99%

“…Most studies dealing with the influence of clouds on solar radiation in WA have therefore been limited to Niamey, in the Sahel region (e.g. Bouniol et al ., ; Bourgeois et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Spatio‐temporal variability of cloud cover types in West Africa with satellite‐based and reanalysis data

Danso

Anquetin

Diedhiou

et al. 2019

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

This study aims to understand and document the occurrence and variability of cloud cover types in West Africa (WA). Investigations are carried out with a 10‐year hourly record of two cloud data products: CERES passive satellite observations and ERA5 reanalysis. The seasonal evolutions of high (HCC), middle (MCC), low (LCC) and total (TCC) cloud cover are examined. Both products agree on the seasonal and spatial occurrence of cloud cover, although CERES presents lower values of cloud fraction than ERA5 which is partly attributed to the inability of the satellite sensor to detect optically thin clouds in the atmosphere. Southern WA is found to be cloudier than other parts of the region in all seasons with mean TCC fractions of 70 and 80% for CERES and ERA5 respectively during the monsoon season. In all seasons, the presence of LCC over large areas of the Sahel/Sahara region is noted in the CERES product. This could be due to a possible misinterpretation of Saharan dust as low clouds which may have thus, caused it to overestimate the occurrences and fractions of LCC over this region. Northern WA is associated with higher frequencies of no cloud occurrence events, unlike the south where cloudless skies are rarely observed. Furthermore, in southern WA, overcast conditions of LCC are observed for a significant number of times (up to 20% of the time during the rainy season in CERES and 40% in ERA5). The climatology of cloud cover presented in this study could be useful for the planning of solar energy projects.

show abstract

“…Nazaryan et al (2008) studied the spatial and temporal variations of global cirrus based on CALIPSO. Bouniol et al (2012) and Stein et al (2011) studied the cloud structure in West Africa. Medeiros et al (2010) found that the vertical distribution of low-level cloud height is consistent with observations from the Rain in Cumulus over the Ocean (RICO) field study.…”

Section: Introductionmentioning

confidence: 99%

Low-Level Cloud Response to the Gulf Stream Front in Winter Using CALIPSO*

et al. 2014

View full text Add to dashboard Cite

A sharp sea surface temperature front develops between the warm water of the Gulf Stream and cold continental shelf water in boreal winter. This front has a substantial impact on the marine boundary layer. The present study analyzes and synthesizes satellite observations and reanalysis data to examine how the sea surface temperature front influences the three-dimensional structure of low-level clouds. The CloudAerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite captures a sharp lowlevel cloud transition across the Gulf Stream front, a structure frequently observed under the northerly condition. Low-level cloud top (,4 km) increases by about 500 m from the cold to the warm flank of the front. The sea surface temperature front induces a secondary low-level circulation through sea level pressure adjustment with ascending motion over the warm water and descending motion over cold water. The secondary circulation further contributes to the cross-frontal transition of low-level clouds. Composite analysis shows that surface meridional advection over the front plays an important role in the development of the marine atmospheric boundary layer and low-level clouds. Under cold northerly advection over the Gulf Stream front, strong near-surface instability leads to a well-mixed boundary layer over the Gulf Stream, causing southward deepening of low-level clouds across the sea surface temperature front. Moreover, the front affects the freezing level by transferring heat to the atmosphere and therefore influences the cross-frontal variation of the cloud phase.

show abstract

Diurnal and Seasonal Cycles of Cloud Occurrences, Types, and Radiative Impact over West Africa

Cited by 58 publications

References 63 publications

A one‐year study of the diurnal cycle of meteorology, clouds and radiation in the West African Sahel region

A one‐year study of the diurnal cycle of meteorology, clouds and radiation in the West African Sahel region

Spatio‐temporal variability of cloud cover types in West Africa with satellite‐based and reanalysis data

Low-Level Cloud Response to the Gulf Stream Front in Winter Using CALIPSO*

Contact Info

Product

Resources

About