The second session on assimilation and impact of AMVs in NWP focused on recent evaluation studies using operational numerical forecasts in different regions world-wide. From the USA Paul Menzel presented results of a case study into the sensitivity of the Eta data assimilation system (EDAS) to radiosonde observations, wind estimates from ACARS (Aircraft Communications Addressing and Reporting S...

TheAdvanced Regional Prediction System (ARPS) is used to simulate a tornadic mesovortex with the aim of understanding the associated tornadogenesis processes. The mesovortex was one of two tornadic mesovortices spawned by a mesoscale convective system (MCS) that traversed southwestern and central Oklahoma on 8–9 May 2007. The simulation used 100-m horizontal grid spacing, and is nested within t...

A 3D-variational data assimilation scheme for a quasi-geostrophic channel model (Morss, 1998) is used to study the structure of the background error and its relationship to the corresponding bred vectors. The “true” evolution of the model atmosphere is defined by an integration of the model and “rawinsonde observations” are simulated by randomly perturbing the true state at fixed locations. Cas...

3 Data assimilation leads naturally to a Bayesian formulation in which the posterior probability 4 distribution of the system state, given all the observations on a time window of interest, 5 plays a central conceptual role. The aim of this paper is to use this Bayesian posterior 6 probability distribution as a gold standard against which to evaluate various commonly used 7 data assimilation al...

33 34 The ARPS model is used to simulate a tornadic mesovortex with the aim of 35 understanding the associated tornadogenesis processes. The mesovortex was one of two tornadic 36 mesovortices spawned by a mesoscale convective system (MCS) that traversed southwest and 37 central Oklahoma on 8-9 May 2007. The simulation used 100-m horizontal grid spacing, and is 38 nested within two outer grids w...

[1] The ARPS 3DVAR data assimilation system is enhanced and used for the first time to assimilate airborne Doppler radar wind observations. It is applied to Hurricane Ike (2008), where radar observations taken along four flight legs through the hurricane vortex 14 to 18 h before it made landfall are assimilated. An optimal horizontal de-correlation scale for the background error is determined t...

In this two-part paper, the impact of level-II Weather Surveillance Radar-1988 Doppler (WSR-88D) reflectivity and radial velocity data on the prediction of a cluster of tornadic thunderstorms in the Advanced Regional Prediction System (ARPS) model are studied. Radar reflectivity data are used primarily in a cloud analysis procedure that retrieves the amount of hydrometeors and adjusts in-cloud ...

Using the 3-Dimensional Variational Analysis data assimilation scheme and the Pennsylvania State University (PSU)/National Center for Atmospheric Research (NCAR) Mesoscale Model 5 (MM5) as configured and run operationally by the Air Force Weather Agency (AFWA) in the European theater, input observations were denied in three different categories: total, upper air, and surface observation denial....

A three-dimensional variational (3DVAR) scheme is developed for retrieving three-dimensional moisture in the atmosphere from slant-path measurements of a hypothetical ground-based global positioning system (GPS) observation network. It is assumed that the observed data are in the form of slant-path water vapor (SWV), which is the integrated water vapor along the slant path between the ground re...