Ristic convection scheme at WRF model

Ristic convection scheme contributed by Weather2 has been accepted and tested in WRF version 4.4.1. The code passed all stages of testing. The code is in the public domain and can be downloaded from the official Weather2 Github repository:

Release WRF Version 4.4.1 (Ristic micro+conv) · Weather2/WRF (github.com)
https://github.com/Weather2/WRF/releases/tag/v4.4.1

Overview

To improve cloud and precipitation forecast we developed new convective scheme and we implemented it in WRF model. Convective clouds have always been a great challenge for meteorologists, among other things, due to the inability to describe processes of cloud formation, development and dissipation in a satisfactory manner. Applying parameterization in to the models has lead to simpler form of equations that could be used in practice, and thus different types of convective schemes in numerical weather prediction models appeared. Proposed convective scheme is based on basic elements that affect convection such as convective available potential energy (CAPE), vertical velocity at the base of the cloud, the amount of ice in the cloud and important assumptions. The scheme is conceived as a wet vertical turbulent diffusion and a logical continuation of dry vertical planetary boundary layer (PBL) turbulent diffusion. The scheme determines the vertical levels in the model where the convective cloud begins and ends. Integrated in the model this scheme showed good results in practice.

A complete description is now found in Ristic I., Kordic I., April 2022: Convective velocity scale and its application in convective parameterization
which can be found at ResearchGate:
https://www.researchgate.net/publication/359716993_Convective_velocity_scale_and_its_application_in_convective_parametrization

Contact

Please use this address for direct questions/comments about this page:

Mr. Ivan Ristic
ivanr@weather2.rs

Description of changes

Registry/Registry.EM_COMMON

phys/Makefile

phys/module_cu_ristic.F

phys/module_cumulus_driver.F

phys/module_physics_addtendc.F

phys/module_physics_init.

User’s guide

Users are encouraged to use WRF version 4.4.1 or upcoming versions.

In order to use Ristic microphysics and convection schemes after downloading and compiling the code, the following changes to namelist.input are required:

mp_physics = 150,

cu_physics = 147,

Fallowing changes are recommended:

ra_lw_physics                 = 99, 1, 1,

ra_sw_physics                 = 99, 1, 1,

Example of the namelist.input for one domain for the physics part:

&physics

!——————- MICROPHYSICS ———————-

mp_physics                    = 150,

!——————- RADIATION ————————-

ra_lw_physics                 = 99,

ra_sw_physics                 = 99,

radt                          = 60,

icloud                        = 0,

co2tf                         = 1,

!——————- SURFACE LAYER ———————

sf_sfclay_physics             = 1,

iz0tlnd                       = 0,

isftcflx                      = 0,

!——————- LSM ——————————-

sf_surface_physics            = 4,

num_soil_layers               = 4,

num_land_cat                  = 21,

!——————- PBL ——————————-

bl_pbl_physics                = 1,

bldt                          = 0,

!——————- CUMULUS —————————

cu_physics                    = 147,

cudt                          = 0,

Test results

Bellow are presented two real test cases in which the applied microphysics and convection scheme was tested.

First test situation ( Naples, Italy 11th August, 2016)
Night summer convection developed in Tyrrhenian sea moved slowly toward east and arrived around 12 UTC to the city of Naples, (Figure 1). Convection and clouds over Naples can be seen both on the cloud maps from the model as well as from satellite images and they correspond well (Figure 2 and Figure 3).

Figure 1. (WRF Ristic micro+conv scheme, precipitation from 06-12 UTC, 11.8.2016.)
Figure 2. (WRF Ristic micro+conv scheme clouds at 12 UTC, 11.8.2016.)

Figure 3. Satellite cloud picture at 11.08.2016 at 10 UTC

(https://weather.us/satellite/europe/satellite-hd-15min/20160811-1000z.html)

Second test situation (Sicily, Italy 8th September, 2017)

Mix of stratiform and convective clouds formed over Mediterranean sea (between Sicily and Africa) and caused precipitation over Sicily that lasted for couple of hours.This situation was forecasted well with proposed scheme (Figure 4). The cloud cover from the model with proposed convective scheme (Figure 5) correspond well with the satellite image (Figure 6).

Figure 4. (WRF Ristic micro+conv scheme, precipitation from 12-18 UTC, 8.9.2017.)
Figure 5. (WRF Ristic micro+conv scheme clouds at 12 UTC, 8.9.2017.) 

Figure 6. (Satelite image 12 UTC , 8.9.2017.)

https://weather.us/satellite/europe/satellite-hd-15min/20170908-1200z.html