Convection in PIDCAP part I: Evaluating LAM convection

Autor(en)

Leopold Haimberger, Michael Hantel

Abstrakt

One goal of BALTEX is to quantify the energy and water cycle over the Baltic region through LAMs. The convective components of these cycles cannot be explicitly modelled and thus are parameterized. In this two-part paper we consider the total convective heat flux c as key sub-gridscale quantity. We use it, in the present Part I, for a model intercomparison. We have four European LAMs (EM, BM, REMO and HIRLAM) at our disposal and run them, both in the prognostic and in the diagnostic mode, for a 9-day target period (Aug/Sep 1995) located within the convectively active part of PIDCAP. We find in the prognostic mode that the vertical profile of c is in most cases characterized by boundary layer convection. The flux is strongest at the surface (c ≈ - 100 W/m²) and becomes weaker at higher levels. In three deep convection experiments we select columns with a maximum number of lightning events, a maximum precipitation rate and a maximum c. These events are rare (order of 1 % of all columns) but show free atmosphere fluxes of up to c ≈ -300 W/m². This result is supported by the net condensation rate CON which is complementary to c. The differences between the LAMs in terms of c and CON are small but significant. From the analysed gridscale fields of the LAMs we further derive, in the diagnostic mode, profiles of c, CON and other convective parameters and compare them with their forecast equivalents. The comparison is best for the HIRLAM model. This suggests that the physical package of HIRLAM, due to its hybrid convection scheme STRACO, may be a bit more realistic than those of EM, BM and REMO. Conclusion of Part I is that the total convective heat flux c is useful to make the model physics comparable across LAMs. In Part II, the problem how to diagnose c from observed gridscale data will be reviewed.

Organisation(en)

Institut für Meteorologie und Geophysik

Journal

Meteorology and Atmospheric Physics

Band

77

Seiten

85-98

Anzahl der Seiten

14

ISSN

0177-7971

DOI

https://doi.org/10.1007/s007030170019

Publikationsdatum

2001

Peer-reviewed

Ja

ÖFOS 2012

1030 Physik, Astronomie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/6d818389-5329-4a5c-8aef-0ce2f0b19be9