Quantifying the Contribution of Different Cloud Types to the Radiation Budget in Southern West Africa

The contribution of cloud to the radiation budget of southern West Africa (SWA) is poorly understood and yet it is important for understanding regional monsoon evolution and for evaluating and improving climate models, which have large biases in this region. Radiative transfer calculations applied to atmospheric profiles obtained from the CERES– CloudSat–CALIPSO–MODIS (CCCM) dataset are used to investigate the effects of 12 different cloud types (defined by their vertical structure) on the regional energy budget of SWA (5°–10°N, 8°W–8°E) during June–September. We show that the large regional mean cloud radiative effect in SWA is due to nonnegligible contributions from many different cloud types; eight cloud types have a cloud fraction larger than 5% and contribute at least 5% of the regional mean shortwave cloud radiative effect at the top of the atmosphere. Low clouds, which are poorly observed by passive satellite measurements, were found to cause net radiative cooling of the atmosphere, which reduces the heating from other cloud types by approximately 10%. The sensitivity of the radiation budget to underestimating low-cloud cover is also investigated. The radiative effect of missing low cloud is found to be up to approximately −25 W m−2 for upwelling shortwave irradiance at the top of the atmosphere and 35 W m−2 for downwelling shortwave irradiance at the surface.

[1]  L. Oreopoulos,et al.  New insights about cloud vertical structure from CloudSat and CALIPSO observations , 2017, Journal of geophysical research. Atmospheres : JGR.

[2]  G. Mace,et al.  Cloud occurrences and cloud radiative effects (CREs) from CERES‐CALIPSO‐CloudSat‐MODIS (CCCM) and CloudSat radar‐lidar (RL) products , 2017, Journal of geophysical research. Atmospheres : JGR.

[3]  Jonathan P. Taylor,et al.  The Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa Field Campaign: Overview and Research Highlights , 2017 .

[4]  P. Knippertz,et al.  Why Do Global Climate Models Struggle to Represent Low-Level Clouds in the West African Summer Monsoon? , 2017 .

[5]  B. Adler,et al.  Nocturnal low-level clouds over southern West Africa analysed using high-resolution simulations , 2017 .

[6]  Guosheng Liu,et al.  Assessing the Radiative Effects of Global Ice Clouds Based on CloudSat and CALIPSO Measurements , 2016 .

[7]  R. Allan,et al.  A multisatellite climatology of clouds, radiation, and precipitation in southern West Africa and comparison to climate models , 2016 .

[8]  P. Field,et al.  The Impact of Two Coupled Cirrus Microphysics–Radiation Parameterizations on the Temperature and Specific Humidity Biases in the Tropical Tropopause Layer in a Climate Model , 2016 .

[9]  A. Bodas‐Salcedo,et al.  Large contribution of supercooled liquid clouds to the solar radiation budget of the Southern Ocean , 2016 .

[10]  M. Miller,et al.  A one‐year study of the diurnal cycle of meteorology, clouds and radiation in the West African Sahel region , 2016 .

[11]  R. Hogan,et al.  The representation of the West African monsoon vertical cloud structure in the Met Office Unified Model: an evaluation with CloudSat , 2015 .

[12]  P. Field,et al.  The possible role of local air pollution in climate change in West Africa , 2015 .

[13]  A. Fink,et al.  Satellite‐based climatology of low‐level continental clouds in southern West Africa during the summer monsoon season , 2015 .

[14]  R. Gillies,et al.  Significant impacts of radiation physics in the Weather Research and Forecasting model on the precipitation and dynamics of the West African Monsoon , 2015, Climate Dynamics.

[15]  C. Taylor,et al.  The scale dependence and structure of convergence fields preceding the initiation of deep convection , 2014 .

[16]  O. O. Jegede,et al.  The DACCIWA project: Dynamics-aerosol-chemistry-cloud interactions in West Africa , 2014 .

[17]  G. Tselioudis,et al.  Global Weather States and Their Properties from Passive and Active Satellite Cloud Retrievals , 2013 .

[18]  Jean-Luc Redelsperger,et al.  The Present and Future of the West African Monsoon: A Process-Oriented Assessment of CMIP5 Simulations along the AMMA Transect , 2013 .

[19]  P. Knippertz,et al.  The role of moist convection in the West African monsoon system: Insights from continental‐scale convection‐permitting simulations , 2013 .

[20]  Anthony J. Baran,et al.  A new high- and low-frequency scattering parameterization for cirrus and its impact on a high-resolution numerical weather prediction model , 2013 .

[21]  P. Knippertz,et al.  Formation and Maintenance of Nocturnal Low-Level Stratus over the Southern West African Monsoon Region during AMMA 2006 , 2013 .

[22]  S. Bony,et al.  The ‘too few, too bright’ tropical low‐cloud problem in CMIP5 models , 2012 .

[23]  J. Quaas,et al.  Evaluation of Clouds and Precipitation in the ECHAM5 General Circulation Model Using CALIPSO and CloudSat Satellite Data , 2012 .

[24]  M. Miller,et al.  The Radiation Budget of the West African Sahel and Its Controls: A Perspective from Observations and Global Climate Models , 2012 .

[25]  E. O'connor,et al.  Diurnal and Seasonal Cycles of Cloud Occurrences, Types, and Radiative Impact over West Africa , 2012 .

[26]  R. Hogan,et al.  The vertical cloud structure of the West African monsoon: A 4 year climatology using CloudSat and CALIPSO , 2011 .

[27]  P. Knippertz,et al.  Ultra‐low clouds over the southern West African monsoon region , 2011 .

[28]  David M. Winker,et al.  Improvements of top-of-atmosphere and surface irradiance computations with CALIPSO-, CloudSat-, and MODIS-derived cloud and aerosol properties , 2011 .

[29]  John M. Haynes,et al.  COSP: Satellite simulation software for model assessment , 2011 .

[30]  Sunny Sun-Mack,et al.  CERES Edition-2 Cloud Property Retrievals Using TRMM VIRS and Terra and Aqua MODIS Data—Part I: Algorithms , 2011, IEEE Transactions on Geoscience and Remote Sensing.

[31]  F. Giorgi,et al.  Progress in regional downscaling of west African precipitation , 2011 .

[32]  Patrick Minnis,et al.  Relationships among cloud occurrence frequency, overlap, and effective thickness derived from CALIPSO and CloudSat merged cloud vertical profiles , 2010 .

[33]  Jan Polcher,et al.  AMMA-Model Intercomparison Project , 2010 .

[34]  R. Marchand,et al.  A description of hydrometeor layer occurrence statistics derived from the first year of merged Cloudsat and CALIPSO data , 2009 .

[35]  Thomas Jung,et al.  Understanding the local and global impacts of model physics changes: an aerosol example , 2008 .

[36]  S. Dewitte,et al.  The Geostationary Earth Radiation Budget Edition 1 data processing algorithms , 2008 .

[37]  A. Fink,et al.  Nocturnal stratiform cloudiness during the West African monsoon , 2007 .

[38]  K. Cook,et al.  Coupled Model Simulations of the West African Monsoon System: Twentieth- and Twenty-First-Century Simulations , 2006 .

[39]  D. Corney,et al.  The Geostationary Earth Radiation Budget project , 2005 .

[40]  Jean-Jacques Morcrette,et al.  Influence of aerosol climatology on forecasts of the African Easterly Jet , 2005 .

[41]  John E. Harries,et al.  Determining cloud forcing by cloud type from geostationary satellite data , 2005 .

[42]  S. Kato Computation of Domain-Averaged Shortwave Irradiance by a One-Dimensional Algorithm Incorporating Correlations between Optical Thickness and Direct Incident Radiation , 2003 .

[43]  J. Grist,et al.  The atmospheric circulation over West Africa and equatorial Africa , 2003 .

[44]  William B. Rossow,et al.  Cloud Vertical Structure and Its Variations from a 20-Yr Global Rawinsonde Dataset , 2000 .

[45]  Martin Wild,et al.  The radiative impact of a simple aerosol climatology on the Hadley Centre atmospheric GCM , 1998 .

[46]  A. Slingo,et al.  Studies with a flexible new radiation code. I: Choosing a configuration for a large-scale model , 1996 .

[47]  Jonathan P. Taylor,et al.  Studies with a flexible new radiation code. II: Comparisons with aircraft short‐wave observations , 1996 .

[48]  D. Hartmann,et al.  The Effect of Cloud Type on Earth's Energy Balance: Global Analysis , 1992 .