 |
| Titel |
How does the "too frequent, too light" precipitation bias in climate models affect the precipitation response to future warming? |
| VerfasserIn |
Christopher Terai, Peter Caldwell, Stephen Klein |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145747
|
| Publikation (Nr.) |
 EGU/EGU2017-9717.pdf |
|
|
|
|
|
| Zusammenfassung |
| Longstanding biases in climate model precipitation cast doubt on predictions of future
precipitation change. Precipitation is too frequent and too light in many climate models.
Errors in the intensity and frequency of precipitation have an impact on cloud evolution
and latent heat distribution within the atmosphere and therefore have a potentially
important impact on a model’s climate and predictions of future climate change. Past
studies have suggested that the too frequent/too light bias affects models’ ability
to achieve extreme precipitation rates by inhibiting the buildup of moisture and
instability and suppressing convective organization in climate models. In this study, we
characterize more precisely the conditions under which these frequent, light rain
events occur and investigate how a simple modification to a prototype model of the
Department of Energy’s Accelerated Climate Model for Energy, which alleviates
the frequent and light precipitation, impacts the model’s precipitation response to
warming.
We find that light precipitation occurs globally, but primarily in oceanic trade cumulus
regions, where daily ‘drizzle’ frequencies can exceed 90%. About 80% of this drizzle comes
from the convective scheme. As expected, drizzle falls primarily from clouds in subsiding
regions with modest precipitable water. With the original and a modified model where the
light rain is suppressed, we examine the dynamic and thermodynamic response of the climate
to reduced drizzle to test whether suppressing convective drizzle leads to changes in the
precipitation response to a simple 4K increase in sea surface temperatures. We test whether
the suppression of the light precipitation affects how and whether precipitation events
become more organized with warming and hence affect changes in extreme rainfall
rates.
This work was conducted under the auspices of the U.S. Department of Energy by
Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. IM release:
LLNL-ABS-717198. |
|
|
|
|
|
|