The study explored the ability of four cumulus parameterization schemes (CPSs) from Weather and Research Forecasting model (WRF) to simulate mean rainfall patterns, number of rainy days (NRD) and vertically integrated moisture flux (VIMF) during the composite of wet years for the core rainfall seasons of March-April-May (MAM; 1989, 1998 and 2012) and Octo-ber-November-December (OND; 1997, 2006 and 2015) seasons. The CPSs used were Kain-Fritsch (KF), Kain-Fritsch with a moisture-advection based trigger function (KFT), Grell Dévényi (GRELL) and Betts Miller Janjic (BML). The simulations by the GRELL and KF schemes were clearly separated by the dry and wet rainfall gradient in the simulations. For example, the GRELL scheme rainfall simulations were drier over the eastern parts of the region bet-ter. The KF and KFT schemes generated wetter rainfall conditions mainly con-fined to the western parts of the region. The BML scheme simulations were not consistent with the observations. The western and eastern parts of the region were characterized by more and fewer NRD, in both the KF and GRELL schemes. The root mean square error (RMSE) and spatial correlation by KF scheme was 2 mm/day and 0.6. The GRELL scheme however simulated low correlation of 0.45 and RMSE of about 3.0 mm/day over most of the sub-domains. The moisture convergence biases were found to be larger conti-nentally and parts of the nearby Indian Ocean. The persisting rainfall biases constituting of too wet and dry conditions were associated with the KF and GRELL cumulus schemes. The findings from the current study are very funda-mental for the improvement of numerical weather prediction (NWP) tools and cumulus modification processes over the region. The accurate and higher skill rainfall forecasts would provide early warning information for disaster risk re-duction and the related risks on the livelihoods.
References
[1]
Opijah, F.J., Mutemi, J.N. and Ogallo, L.A. (2014) Application of the Ems-Wrf Model in Dekadal Rainfall Prediction over the EA Region. African Journal of the Physical Sciences, 1, 1.
[2]
Kang, I.S., Jin, K., Wang, B., Lau, K.M., Shukla, J., Krishnamurthy, V., Meehl, G., et al. (2002) Intercomparison of the Climatological Variations of Asian Summer Monsoon Precipitation Simulated by 10 GCMs. Climate Dynamics, 19, 383-395. https://doi.org/10.1007/s00382-002-0245-9
[3]
Huang, D.Q., Zhu, J., Zhang, Y.C. and Huang, A.N. (2013) Uncertainties on the Simulated Summer Precipitation over Eastern China from the CMIP5 Models. Journal of Geophysical Research: Atmospheres, 118, 9035-9047. https://doi.org/10.1002/jgrd.50695
[4]
Giorgi, F. and Bates, G.T. (1989) The Climatological Skill of a Regional Model over Complex Terrain. Monthly Weather Review, 117, 2325-2347. https://doi.org/10.1175/1520-0493(1989)117<2325:TCSOAR>2.0.CO;2
[5]
Kim, I.W., Oh, J., Woo, S. and Kripalani, R.H. (2018) Evaluation of Precipitation Extremes over the Asian Domain: Observation and Modelling Studies. Climate Dynamics, 1-26. https://doi.org/10.1007/s00382-018-4193-4
[6]
Dai, A. (2006) Precipitation Characteristics in Eighteen Coupled Climate Models. Journal of Climate, 19, 4605-4630. https://doi.org/10.1175/JCLI3884.1
[7]
Ogwang, A.B., Chen, H., Tan, G., Ongoma, V. and Ntwali, D. (2015a) Diagnosis of East African Climate and the Circulation Mechanisms Associated with Extreme Wet and Dry Events: A Study Based on RegCM4. Arabian Journal of Geosciences, 8, 10255-10265.
[8]
Ogwang, B.A., Ongoma, V., Xing, L. and Faustin, K.O. (2015b) Influence of Mascarene High and Indian Ocean Dipole on East African Extreme Weather Events. Geographica Pannonica, 19, 64-72.
[9]
Pohl, B., Cre’tat, J. and Camberlin, P. (2011) Testing WRF Capability in Simulating the Atmospheric Water Cycle over Equatorial East Africa. Climate Dynamics, 37, 1357-1379. https://doi.org/10.1007/s00382-011-1024-2
[10]
Anyah, R. and Semazzi, F.H.M (2006) Climate Variability over the Greater Horn of Africa Based on NCAR AGCM Ensemble. Theoretical and Applied Climatology, 86, 39-62. https://doi.org/10.1007/s00704-005-0203-7
[11]
Segele, Z.T., Lance, M.L. and Lamba, P.J. (2009) Evaluation and Adaptation of a Regional Climate Model for the Horn of Africa: Rainfall Climatology and Interannual Variability. International Journal of Climatology, 29, 47-65. https://doi.org/10.1002/joc.1681
[12]
Kerandi, N.M., Laux, P., Arnault, J. and Kunstmann, H. (2017) Performance of the WRF Model to Simulate the Seasonal and Interannual Variability of Hydrometeorological Variables in East Africa: A Case Study for the Tana River Basin in Kenya. Theoretical and Applied Climatology, 130, 401-418. https://doi.org/10.1007/s00704-016-1890-y
[13]
Mariotti, L., Coppola, E., Sylla, M.B., Giorgi, F. and Piani, C. (2011) Regional Climate Model Simulation of Projected 21st Century Climate Change over an All-Africa Domain: Comparison Analysis of Nested and Driving Model Results. Journal of Geophysical Research: Atmospheres, 116, D15111. https://doi.org/10.1029/2010JD015068
[14]
Anyah, R.O. and Semazzi, F.H.M. (2007) Variability of East African Rainfall Based on Multiyear RegCM3 Simulations. International Journal of Climatology, 27, 357-371. https://doi.org/10.1002/joc.1401
[15]
Davis, N., Bowden, J., Semazzi, F.H.M., Xie, L. and Önol, B. (2009) Customization of RegCM3 Regional Climate Model for Eastern Africa and a Tropical Indian Ocean Domain. Journal of Climate, 22, 3595-3616. https://doi.org/10.1175/2009JCLI2388.1
[16]
Druyan, L., Fulakeza, M.P. and Noble, E. (2009) Regional Climate Model Simulation of the AMMA Special Observing Period #3 and the Pre-Helene Easterly Wave. Meteorology and Atmospheric Physics, 105, 191-210. https://doi.org/10.1007/s00703-009-0044-5
[17]
Vogel, P., Knippertz, P., Fink, A.H., Schlueter, A. and Gneiting, T. (2018) Skill of Global Raw and Postprocessed Ensemble Predictions of Rainfall over Northern Tropical Africa.
[18]
Fosser, G., Khodayar, S. and Berg, P. (2015) Benefit of Convection Permitting Climate Model Simulations in the Representation of Convective Precipitation. Climate Dynamics, 44, 45-60. https://doi.org/10.1007/s00382-014-2242-1
[19]
Wang, W. and Seaman, N. (1997) A Comparison Study of Convective Parameterization Schemes in a Mesoscale Model. Monthly Weather Review, 125, 252-278. https://doi.org/10.1175/1520-0493(1997)125<0252:ACSOCP>2.0.CO;2
[20]
Gallus, W.A. (1999) Eta Simulations of Three Extreme Precipitation Events: Sensitivity to Resolution and Convective Parameterization. Weather and Forecasting, 14, 405-426. https://doi.org/10.1175/1520-0434(1999)014<0405:ESOTEP>2.0.CO;2
[21]
Leung, L.R., Qian, Y., Bian, X., Washington, W.M., Han, J. and Roads, J.O. (2004) Mid-Century Ensemble Regional Climate Change Scenarios for the Western United States. Climatic Change, 62, 75-113. https://doi.org/10.1023/B:CLIM.0000013692.50640.55
[22]
Chen, L., Liang, X.Z., DeWitt, D., Samel, A.N. and Wang, J.X. (2016) Simulation of Seasonal US Precipitation and Temperature by the Nested CWRF-ECHAM System. Climate Dynamics, 46, 879-896.https://doi.org/10.1007/s00382-015-2619-9
[23]
Mutemi, J.N., Ogallo, L.A., Krishnamurti, T.N., Mishra, A.K. and Kumar, T.S.V. (2007) Multimodel Based Superensemble Forecasts for Short and Medium Range NWP over Various Regions of Africa. Meteorology and Atmospheric Physics, 95, 87-113. https://doi.org/10.1007/s00703-006-0187-6
[24]
Endris, H.S., Omondi, P., Jain, S., Lennard, C., Hewitson, B., Chang’a, L., Awange, J., Dosio, A., Ketiem, P., Nikulin, G., Panitz, H., Buchner, M., Stordal, F. and Tazalika, L. (2013) Assessment of the Performance of CORDEX Regional Climate Models in Simulating Eastern Africa Rainfall. Journal of Climate, 26, 8453-8475. https://doi.org/10.1175/JCLI-D-12-00708.1
[25]
Anyah, R.O., Semazzi, F.H.M. and Xie, L. (2006) Simulated Physical Mechanisms Associated with Climate Variability over Lake Victoria Basin in East Africa. Monthly Weather Review, 134, 3588-3609. https://doi.org/10.1175/MWR3266.1
[26]
Ratna, S.B., Ratnam, J.V., Behera, S.K., Ratnam, J.V., Rautenbach, C.W., Lennard, J.-J., Luo, Y., Masumoto, K. and Yamagata, T. (2014) Performance Assessment of Three Convective Parameterization Schemes in WRF for Downscaling Summer Rainfall over South Africa. Climate Dynamics, 42, 2931-2953.
[27]
Crétat, J., Pohl, B., Carmela, C.S., Vigaudd, N. and Yves, R. (2015) An Original Way to Evaluate Daily Rainfall Variability Simulated by a Regional Climate Model: The Case of South African Austral Summer Rainfall. International Journal of Climatology, 35, 2485-2502. https://doi.org/10.1002/joc.4155
[28]
Skamarock, W.C., Klemp, J.B., Dudhia, J., Gill, D.O., Barker, D.M., Duda, M., Huang, H., Wang, W. and Powers, J.G. (2008) A Description of the Advanced Research WRF Version 3.
[29]
Skamarock, W.C., Klemp, J., Dudhia, J., Gill, D.O., Barker, D.M., Wang, W. and Powers, J.G. (2005) A Description of the Advanced Research WRF Version 2.
[30]
Uppala, S., Dee, D., Kobayashi, S., Berrisford, P. and Simmons, A. (2008) Towards a Climate Data Assimilation System: Status Update of ERA-Interim. ECMWF Newsletter, No. 115, 12-18.
[31]
Chen, F. and Dudhia, J. (2001) Coupling an Advanced Land-Surface/Hydrology Model with the Penn State/NCAR MM5 Modeling System. Part 1: Model Description and Implementation. Monthly Weather Review, 129, 569-585. https://doi.org/10.1175/1520-0493(2001)129<0569:CAALSH>2.0.CO;2
[32]
Segele, Z.T., Lance, M.L. and Aondover, A.T. (2015) Sensitivity of Horn of Africa Rainfall to Regional Sea Surface Temperature Forcing. Journal of Climate, 3, 365-390. https://doi.org/10.3390/cli3020365
[33]
Giorgi, F. and Shields, C. (1999) Tests of Precipitation Parameterizations Available in Latest Version of NCAR Regional Climate Model (RegCM) over Continental United States. Journal of Geophysical Research, 104, 6353-6375. https://doi.org/10.1029/98JD01164
[34]
Omondi, A.P. (2010) The Teleconnections between Decadal Rainfall Variability and Global Sea Surface Temperatures and Simulation of Future Climate Scenarios over East Africa. PhD Thesis, University of Nairobi, Nairobi.
[35]
Otieno, V.O. and Anyah, R.O. (2012) Effects of Land Use Changes on Climate in the Greater Horn of Africa. Climate Research, 52, 77-95. https://doi.org/10.3354/cr01050
[36]
Hong, S.Y. and Lim, J.O.J. (2006) The WRF Single-Moment 6-Class Microphysics Scheme (WSM6). Journal of the Korean Meteorological Society, 42, 129-151.
[37]
Hong, S.Y., Noh, Y. and Dudhia, J. (2006) A New Vertical Diffusion Package with an Explicit Treatment of Entrainment Processes. Monthly Weather Review, 134, 2318-2341. https://doi.org/10.1175/MWR3199.1
[38]
Alapaty, K., Herwehe, J.A., Otte, T.L., Nolte, C.G., Bullock, O.R., Mallard, M.S., Kain, J.S. and Dudhia, J. (2012) Introducing Subgrid-Scale Cloud Feedbacks to Radiation for Regional Meteorological and Climate Modeling. Geophysical Research Letters, 39, L24809. https://doi.org/10.1029/2012GL054031
[39]
Ma, L.M. and Tan, Z.M. (2009) Improving the Behavior of the Cumulus Parameterization for Tropical Cyclone Prediction: Convection Trigger. Atmospheric Research, 92, 190-211. https://doi.org/10.1016/j.atmosres.2008.09.022
[40]
Kain, J.S. (2004) The Kain-Fritsch Convective Parameterization: An Update. Journal of Applied Meteorology, 43, 170-181. https://doi.org/10.1175/1520-0450(2004)043<0170:TKCPAU>2.0.CO;2
[41]
Kain, J.S. and Fritsch, J.M. (1992) Role of Convective Trigger Functions in Numerical Forecasts of Mesoscale Convective Systems. Meteorology and Atmospheric Physics, 49, 93-106.
[42]
Grell, G.A. and Devenyi, D. (2002) A Generalized Approach to Parameterizing Convection Combining Ensemble and Data Assimilation Techniques. Geophysical Research Letters, 29, 1-4. https://doi.org/10.1029/2002GL015311
[43]
Grell, G.A. (1993) Prognostic Evaluation of Assumptions Used by Cumulus Parameterizations. Monthly Weather Review, 121, 764-787. https://doi.org/10.1175/1520-0493(1993)121<0764:PEOAUB>2.0.CO;2
[44]
Berhane, F. and Zaitchik, B. (2014) Modulation of Daily Precipitation over East Africa by the Madden-Julian Oscillation. Journal of Climate, 27, 6016-6034. https://doi.org/10.1175/JCLI-D-13-00693.1
[45]
Schneider, T., Smith, K.L., O’Gorman, P.A. and Walker, C.C. (2006) A Climatology of Tropospheric Zonal-Mean Water Vapor Fields and Fluxes in Isentropic Coordinates. Journal of Climate, 19, 5918-5933. https://doi.org/10.1175/JCLI3931.1
[46]
Trenberth, K.E., Fasullo, J.T. and Mackaro, J. (2011) Atmospheric Moisture Transports from Ocean to Land and Global Energy Flows in Reanalyses. Journal of Climate, 24, 4907-4924. https://doi.org/10.1175/2011JCLI4171.1
[47]
Newman, M., Kiladis, G.N., Weickmann, K.M., Ralph, F.M. and Sardeshmukh, P.D. (2012) Relative Contributions of Synoptic and Low-Frequency Eddies to Time-Mean Atmospheric Moisture Transport, Including the Role of Atmospheric Rivers. Journal of Climate, 25, 7341-7361. https://doi.org/10.1175/JCLI-D-11-00665.1
[48]
Funk, C., Verdin, A., Michaelsen, J., Peterson, P., Pedreros, D. and Husak, G. (2015) A Global Satellite Assisted Precipitation Climatology. Earth System Science Data, 8, 401-426. https://doi.org/10.5194/essdd-8-401-2015
[49]
Pohl, B. and Cretat, J. (2014) On the Use of Nudging Techniques for Regional Climate Modeling: Application for Tropical Convection. Climate Dynamics, 43, 1693-1714. https://doi.org/10.1007/s00382-013-1994-3
[50]
Pohl, B., Macron, C. and Monerie, P.A. (2017) Fewer Rainy Days and More Extreme Rainfall by the End of the Century in Southern Africa. Scientific Reports, 7, Article No. 46466. https://doi.org/10.1038/srep46466
[51]
Sun, Y., Dair, A. and Solomon, S. (2006) How Often Does It Rain? Journal of Climate, 19, 916-934. https://doi.org/10.1175/JCLI3672.1
[52]
Salih, A.M., Nadir, A.E., Michael, T. and Qiong, Z. (2018) Characterization of the Sahelian-Sudan Rainfall Based on Observations and Regional Climate Models. Atmospheric Research, 202, 205-218. https://doi.org/10.1016/j.atmosres.2017.12.001
[53]
Philippon, N., Camberlin, P., Moron, V. and Boyard-Michea, J. (2015) Anomalously Wet and Dry Rainy Seasons in Equatorial East Africa and Associated Differences in Intra-Seasonal Characteristics. Climate Dynamics, 45, 1819-1840. https://doi.org/10.1007/s00382-014-2436-6
[54]
Chen, L., Fan, X. and Ma, Z. (2010) Approaches for Assessing Dynamically Downscale Climate. AGU Fall Meeting, San Francisco, 13-17 December 2010, Paper A21G-0181.
[55]
Mlawer, E., Taubman, S., Brown, P., Iacono, M. and Clough, S. (1997) Radiative Transfer for Inhomogeneous Atmosphere: RRTM, a Validated Correlated-K Model for the Long-Wave. Journal of Geophysical Research: Atmospheres, 102, 16663-16682. https://doi.org/10.1029/97JD00237