ǂAn ǂintermediate-complexity model for four-dimensional variational data assimilation including moist processes

Žiga Zaplotnik (Author), Nedjeljka Žagar (Author), N. Gustafsson (Author)

Abstract

This article presents a new Moist Atmosphere Dynamics Data Assimilation Model (MADDAM), an intermediate‐complexity system for four‐dimensional variational (4D‐Var) data assimilation. The prognostic model equations simulate nonlinear moisture advection, precipitation, and the impact of condensational heating on circulation. The 4D‐Var assimilation applies the incremental approach and uses transformed relative humidity as a control variable. In contrast to the model dynamical variables, which are analyzed in multivariate fashion using equatorial wave theory, moisture data are assimilated univariately. MADDAM is applied to study the extraction of wind information from time series of moisture observations in the Tropics, where the lack of wind information is most critical. Results show that wind tracing in the unsaturated atmosphere depends largely on the ability of the assimilation model to resolve spatial gradients in the moisture field, which is determined by the spatial density and accuracy of observations. In the saturated atmosphere, a combined assimilation of moisture and temperature data is shown to improve wind analyses significantly, as the intensity of the condensation process is susceptible to the slightest changes in saturation humidity and thus temperature. Moreover, a perfect‐model 4D‐Var with moisture observations can extract wind information even in precipitating regions and strongly nonlinear flow, provided sufficient observations of humidity gradients are available. MADDAM is envisaged to serve as a testbed for new developments in 4D‐Var assimilation, with a focus on interactions between moist processes and dynamics across many scales.

Keywords

meteorologija;atmosferska dinamika;vlažnost zraka;veter;meteorology;atmospheric dynamics;moisture;wind;

Data

Language:	English
Year of publishing:	2018
Typology:	1.01 - Original Scientific Article
Organization:	UL FMF - Faculty of Mathematics and Physics
UDC:	551.5
COBISS:	373161
ISSN:	0035-9009
Views:	827
Downloads:	432
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary keywords:	meteorologija;atmosferska dinamika;vlažnost zraka;veter;
Embargo end date (OpenAIRE):	2019-06-29
Pages:	str. 1772-1787
Volume:	ǂVol. ǂ144
Issue:	ǂiss. ǂ715
Chronology:	2018
DOI:	10.1002/qj.3338
ID:	10991921