Friday 21 July 2017
Regional climate models at the Hungarian Meteorological Service

A couple of years ago two regional climate models were adapted at the Hungarian Meteorological Service, which are as follows (the main characteristics of the models are presented in Table 1.):

  • The ALADIN-Climate model developed by Météo France on the basis of the ARPEGE-Climat general circulation model;
  • The REMO model originally developed by the Max Planck Institute for Meteorology in Hamburg based on the earlier weather prediction model (Europa Model) of the German Weather Service and the ECHAM4 general circulation model.

Initially, experiments for the past climate were carried out with these regional models in order to investigate and validate their behaviour for a longer period covered by relatively high-density observations. These experiments are executed using "perfect" lateral boundary conditions (with the use of re-analysis data created by using observational information and some short-range numerical predictions). Based on the identified errors, these past climate results provided valuable information for further improvements of the models. In the ensuing model simulations, the large-scale constraints were already ensured by atmospheric or coupled atmosphere-ocean general circulation models instead of re-analysis, since, for the future solely the global climate models are available to drive the RCMs (and the coupling interactions between the global and regional models are of vital interest in understanding the behaviour of regional climate projections). Simulations in the control period were validated against observational data. However, while the former reanalysis-forced outcomes gave some hints for the possible development paths of the regional climate models, GCM-driven results produce combined information about both the global and regional model deficiencies. It has to be remarked, that there is no direct relationship between the performance in the past and future in terms of the ability of describing climatic conditions, nevertheless, in practise the model being better for the past is anticipated to provide a more solid basis for future climate estimations.

While the REMO model simulations were accomplished on 25 km horizontal resolution, in the case of ALADIN-Climate 25 and 10 km resolution were also performed. The coarser resolution experiments covered Central and Eastern Europe, whereas the finer resolution ones were run over a smaller integration domain including the Carpathian Basin. The large-scale information was provided by global model experiments forced by A1B SRES scenario, which is considered to be an "average" estimation for the evolution of the greenhouse gas concentrations by the end of the 21st century. The most important characteristics of the model experiments are summarized in Table 2 and integration domains are shown in Fig. 1.

Table 1: Main characteristics of the applied regional climate models

  ALADIN-Climate 4.5 REMO 5.0
Basic model ingredients Dynamics: ALADIN short-range LAM*
Parameterizations: ARPEGE-Climat AGCM**
Dynamics: Europa Model short-range LAM*
Parameterizations: ECHAM4 AGCM**
Representation of the horizontal spatial derivatives  Spectral  Grid-point
Vertical coordinate system  Hybrid: terrain following + pressure system
Hydrostatic assumption  Hydrostatic
Prognostic variables
  • Temperature,
  • Horizontal wind components,
  • Specific humidity,
  • Surface pressure
  • Temperature,
  • Horizontal wind components,
  • Specific humidity,
  • Cloud-water content,
  • Surface pressure
Temporal schemes Semi-implicit + semi-Lagrange Explicit leapfrog + semi-implicit correction
Physical parameterizations
Radiation Fouquart and Bonnel, Morcrette
Soil model ISBA Warrilow
Soil layers 4 (temperature) and 2 (humidity) 5
Large-scale precipitation and cloudiness  Smith, Ricard and Royer  Sundquist, Roeckner
Convection Bougeault Tiedtke, Nordeng

*   LAM: Limited Area Model
** AGCM: Atmospheric General Circulation Model


 Table 2: Regional climate model simulations at the Hungarian Meteorological Service

  ALADIN-Climate 4.5 REMO 5.0
Experiment AL_ERA_25 AL_ERA_10 AL_ARP_10 REMO_ERA_25 REMO_ECH_25
Period 1961-2000 1961-2000 1961-2100 1961-2000 1951-2100
Horizontal spatial resolution 25 km 10 km 10 km 25 km 25 km
Vertical levels 31 31 31 20 20
Domain Central and Eastern Europe Carpathian Basin Carpathian Basin Central and Eastern Europe Central and Eastern Europe
Lateral boundary conditions (LBCs) ERA-40 re-analyses ERA-40 re-analyses ARPEGE-Climate/OPA AOGCM*** ERA-40 re-analyses ECHAM5/MPI-OM AOGCM***
Resolution of LBCs 125 km 125 km 50 km 125 km 200 km
Emission scenario - - A1B - A1B

*** AOGCM: Atmosphere-Ocean General Circulation Model

 1. ábra

Figure 1: Integration domains: the 25 km (entire image) and 10 km resolution (blue rectangle)
ALADIN-Climate areas on the left, the 25 km resolution domain of REMO on the right