Abstract
Atmospheric moisture content or humidity is an important analysis variable of any meteorological data assimilation system. The humidity analysis can be univariate, using humidity background (normally short-range numerical forecasts) and humidity observations. However, more and more data assimilation systems are multivariate, analyzing humidity together with wind, temperature and pressure. Background error covariances, with unbalanced velocity potential and humidity in the multivariate formulation, are generated from weather research and forecasting model forecasts, collected over a summer rainy season and a winter dry season. The unbalanced velocity potential and humidity related correlations are shown to be significantly larger, indicating more important roles unbalanced velocity potential and humidity play, in the rainy season than that in the dry season. Three cycling data assimilation experiments of two rainfall events in the middle and lower reaches of the Yangtze River are carried out. The experiments differ in the formulation of the background error covariances. Results indicate that only including unbalanced velocity potential in the multivariate background error covariance improves wind analyses, but has little impact on temperature and humidity analyses. In contrast, further including humidity in the multivariate background error covariance although has a slight negative effect on wind analyses and a neutral effect on temperature analyses, but significantly improves humidity analyses, leading to precipitation forecasts more consistent with China Hourly Merged Precipitation Analysis.
Similar content being viewed by others
References
Bannister RN (2008a) A review of forecast error covariance statistics in atmospheric variational data assimilation. I: characteristics and measurements of forecast error covariances. Q J R Meteorol Soc 134:1951–1970
Bannister RN (2008b) A review of forecast error covariance statistics in atmospheric variational data assimilation. II: modelling the forecast error covariance statistics. Q J R Meteorol Soc 134:1971–1996
Barker DM, Huang W, Guo YR, Bourgeois A, Xiao QN (2004) A three-dimensional variational (3DVAR) data assimilation system for use with MM5: implementation and initial results. Mon Weather Rev 132:897–914
Barker DM, Huang XY, Liu Z, Auligné T, Zhang X, Rugg S, Ajjaji R, Bourgeois A, Bray J, Chen Y, Demirtas M, Guo YR, Henderson T, Huang W, Lin HC, Michalakes J, Rizvi S, Zhang X (2012) The weather research and forecasting model’s community variational/ensemble data assimilation system WRFDA. Bull Am Meteorol Soc 93:831–843
Berre L (2000) Estimation of synoptic and mesoscale forecast error covariances in a limited-area model. Mon Weather Rev 128:644–667
Berre L, Ştefănescu SE, Belo-Pereira M (2006) The representation of the analysis effect in three error simulation techniques. Tellus A 58:196–209
Chen Y, Rizvi SR, Huang XY, Min J, Zhang X (2013) Balance characteristics of multivariate background error covariances and their impact on analyses and forecasts in tropical and Arctic regions. Meteorol Atmos Phys 121:79–98
Courtier P, Andersson E, Heckley W, Vasiljevic D, Hamrud M, Hollingsworth A, Rabier F, Fisher M, Pailleux J (1998) The ECMWF implementation of three-dimensional variational assimilation (3D-Var). I: formulation[J]. Q J R Meteorol Soc 124:1783–1807
Derber J, Bouttier F (1999) A reformulation of the background error covariance in the ECMWF global data assimilation system. Tellus A 51:195–221
Fischer C, Montmerle T, Berre L, Auger L, Ştefănescu SE (2005) An overview of the variational assimilation in the ALADIN/France numerical weather-prediction system. Q J R Meteorol Soc 131:3477–3492
Gustafsson N, Berre L, Hörnquist S, Huang X-Y, Lindskog M, Navascues B, Mogensen KS, Thorsteinsson S (2001) Three-dimensional variational data assimilation for a limited area model. Part I: general formulation and the background error constraint. Tellus 53A:425–446
Gustafsson N, Thorsteinsson S, Stengel M, Holm E (2011) Use of a nonlinear pseudo-relative humidity variable in a multivariate formulation of moisture analysis. Q J R Meteorol Soc 137:1004–1018
Huang XY, Xiao Q, Barker DM, Zhang X, Michalakes J, Huang W, Henderson T, Bray J, Chen Y, Ma Z, Dudhia J, Guo Y, Zhang X, Won DJ, Lin HC, Kuo YH (2009) Four-dimensional variational data assimilation for WRF: formulation and Preliminary results[J]. Mon Weather Rev 137:299–314
Ingleby B, Lorenc A, Ngan K, Rawlins R, Jackson D (2011) Improved variational analyses using a nonlinear humidity control variable: formulation and trials. NWP Tech Report
Ingleby B, Lorenc A, Ngan K, Rawlins F, Jackson D (2013) Improved variational analyses using a nonlinear humidity control variable. Q J R Meteorol Soc 139:1875–1887
Krysta M, Rizvi SR, Huang XY (2009) A new formulation of WRFDA analysis control variables. 10th annual WRF users’ workshop, pp 23–26 June 2009
Michel Y, Auligné T (2010) Inhomogeneous background error modeling and estimation over Antarctica. Mon Weather Rev 138:2229–2252
Michel Y, Auligné T, Montmerle T (2011) Heterogeneous convective-scale background error covariances with the inclusion of hydrometeor variables. Mon Weather Rev 139:2994–3015
Parrish DF, Derber JC (1992) The National Meteorological Center’s Spectral Statistical Interpolation analysis system. Mon Weather Rev 120:1747–1763
Shen Y, Zhao P, Pan Y, Yu J (2014) A high spatiotemporal gauge-satellite merged precipitation analysis over China. J Geophys Res Atmos 119:3063–3075
Storto A, Randriamampianina R (2010) Ensemble variational assimilation for the representation of background error covariances in a high-latitude regional model. J Geophys Res 115:D17204. doi:10.1029/2009JD013111
Wang H, Huang XY, Sun J, Xu D, Zhang M, Fan S, Zhong J (2014) Inhomogeneous background error modeling for WRF-Var using the NMC method. J Appl Meteorol Climatol 53:2287–2309
Žagar N, Andersson E, Fisher M (2005) Balanced tropical data assimilation based on a study of equatorial waves in ECMWF short-range forecast errors. Q J R Meteorol Soc 131:987–1011
Acknowledgments
This work is jointly sponsored by the 973 Program (2013CB430102), the Special Fund for Meteorological Scientific Research in Public Interest (GYHY201506002), the National Natural Science Foundation of China (41205082), Quality Control, Fusion and Reanalysis of Meteorological Observations and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).
Author information
Authors and Affiliations
Corresponding author
Additional information
Responsible Editor: F. Mesinger.
Rights and permissions
About this article
Cite this article
Chen, Y., Xia, X., Min, J. et al. Balance characteristics of multivariate background error covariance for rainy and dry seasons and their impact on precipitation forecasts of two rainfall events. Meteorol Atmos Phys 128, 579–600 (2016). https://doi.org/10.1007/s00703-016-0434-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00703-016-0434-4