 |
| Titel |
Results of calibration of the scheme for calculation of multi-layer cloudiness and precipitation for climate models of intermediate complexity |
| VerfasserIn |
Alexey V. Eliseev, Dim Coumou, Alexandr V. Chernokulsky, Vladimir Petoukhov, Stefan Petri |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072715
|
|
|
|
|
|
| Zusammenfassung |
| A scheme for calculation of characteristics of multi–layer cloudiness and precipitation in
climate models of intermediate complexity (EMICs) is presented. It describes three–layer
stratiform cloudiness and single column convective clouds. It distinguishes between ice and
droplet clouds as well. For convective clouds, an universal vertical profile of moisture content
is prescribed based on observations. Precipitation is calculated by using cloud life time which
depends on cloud type and phase as well as on statistics of synoptic and convective
disturbances.
The scheme was calibrated off–line forced by the ERA–40–derived climatology for
1979–2001. A semi–automated procedure was applied by selecting the expert–derived ranges
for parameters of the scheme and attempting to achieve a maximum of the cost function. The
latter accounts for annual means and January and July values for total cloud amounts, total
cloud water and ice path, and total, large–scale, and convective precipitation. Total
cloud amount is evaluated using the ISCCPÂ D2 data, cloud water and ice path is
evaluated against the CERES retrievals, total precipitation is compared to the GPCP
climatology, and the fractions of large–scale and convective precipitation are tested against
ERA–40 data. Parameters of the scheme are sampled by using the Latin Hypercube
sampling.
With the use of the above tuning procedure, the scheme realistically reproduces basic
features of the fields of cloud amounts, cloud heights, cloud water and ice path, and
precipitation. The simulated global and annual mean total cloud amount is 0.57 which agrees
with the respective satellite-retrieved values. In agreement with observations, the highest
stratiform and convective cloud amounts are simulated, respectively, in the regions of storm
tracks and in the tropical regions with moisture convergence. However, subtropical minima of
cloud amounts are too deep in the model. While the overall geographical structure of the
precipitation rate is reproduced realistically by the scheme, precipitation is overestimated in
the subtropics and in the eastern part of Eurasia. In turn, precipitation is underestimated
in the regions of tropical convection. The globally averaged annual precipitation
is 98 cm-yr which is close to the corresponding value obtained from empirical
data.
The three–layer cloud and precipitation scheme has been implemented in the
statistical–dynamical atmosphere model Aeolus which is the part of the a generation of the
Climber–4 EMIC, as well as in the IAP RAS EMIC. |
|
|
|
|
|
|