New indirect radar reflectivity assimilation scheme based on background-dependent hydrometeor retrieval.

[mos3r3n]

A background-dependent hydrometeor retrieval scheme for indirect radar reflectivity assimilation

TYPE: New feature

KEYWORDS: Reflectivity assimilation, hydrometeor retrieval

SOURCE: Haiqin Chen (Nanjing University); Tao Sun (NCAR)

DESCRIPTION OF CHANGES:
Problem:
In the original WRFDA use_radar_rhv scheme, the proportion of the snow and graupel is a fixed value
that is measured by the ratio of coefficients for snow and graupel. In that case, the same snow mixing ratio and graupel mixing ratio are retrieved from reflectivity data.

Solution:
A background-dependent hydrometer retrieval and assimilation scheme is added to assimilate hydrometeors from reflectivity data. In this new scheme, the proportion of each hydrometeor from reflectivity data is diagnosed from background microphysical states. With this scheme, the contribution of each hydrometeor species to the reflectivity varies widely
in different reflectivity ranges and different heights. Therefore, the retrieved hydrometeors are more reasonable, and better hydrometeor analysis can be obtained from reflectivity assimilation.
References:
Chen, H., Gao, J., Wang, Y., Chen, Y., Sun, T., Carlin, J. and Zheng, Y., 2021. Radar reflectivity data assimilation method based on background‐dependent hydrometeor retrieval: Comparison with direct assimilation for real cases. Quarterly Journal of the Royal Meteorological Society, 147(737), pp.2409-2428.
Chen, H., Chen, Y., Gao, J., Sun, T. and Carlin, J.T., 2020. A radar reflectivity data assimilation method based on background-dependent hydrometeor retrieval: An observing system simulation experiment. Atmospheric research, 243, p.105022.

LIST OF MODIFIED FILES: list of changed files (use git diff --name-status master to get formatted list)
M. Registry/registry.var
M. var/da/da_radar/da_radar.f90
M. var/da/da_radar/da_get_innov_vector_radar.inc

TESTS CONDUCTED:

1. The codes are successfully compiled in Chyenne using the intel fortran.
2. Single-time reflectivity assimilation has been tested in Cheyenne and reasonable results are obtained.

[weiwangncar]

The regression test results:

Test Type              | Expected  | Received |  Failed
= = = = = = = = = = = = = = = = = = = = = = = =  = = = =
Number of Tests        : 23           24
Number of Builds       : 60           57
Number of Simulations  : 158           150        0
Number of Comparisons  : 95           86        0

Failed Simulations are: 
None
Which comparisons are not bit-for-bit: 
None

[liujake]

Looks good! Thank you for this contribution!
@weiwangncar Can you also approve it if regtest passes? Then I can merge.

[weiwangncar]

The latest regression test results:

Test Type              | Expected  | Received |  Failed
= = = = = = = = = = = = = = = = = = = = = = = =  = = = =
Number of Tests        : 23           24
Number of Builds       : 60           57
Number of Simulations  : 158           150        0
Number of Comparisons  : 95           86        0

Failed Simulations are: 
None
Which comparisons are not bit-for-bit: 
None