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| Titel |
Land-surface controls on afternoon precipitation diagnosed from observational data: uncertainties and confounding factors |
| VerfasserIn |
B. P. Guillod, B. Orlowsky, D. Miralles, A. J. Teuling, P. D. Blanken, N. Buchmann, P. Ciais, M. Ek, K. L. Findell, P. Gentine, B. R. Lintner, R. L. Scott, B. van den Hurk, S. I. Seneviratne |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 16 ; Nr. 14, no. 16 (2014-08-20), S.8343-8367 |
| Datensatznummer |
250118959
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| Publikation (Nr.) |
 copernicus.org/acp-14-8343-2014.pdf |
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| Zusammenfassung |
| The feedback between soil moisture and precipitation has long been
a topic of interest due to its potential for improving weather and
seasonal forecasts. The generally proposed mechanism assumes
a control of soil moisture on precipitation via the partitioning of
the surface turbulent heat fluxes, as assessed via the evaporative
fraction (EF), i.e., the ratio of latent heat to the sum of latent and
sensible heat, in particular under convective conditions. Our study
investigates the poorly understood link between EF and precipitation
by relating the before-noon EF to the frequency of
afternoon precipitation over the contiguous US, through statistical
analyses of multiple EF and
precipitation data sets. We analyze remote-sensing data products
(Global Land Evaporation: the Amsterdam Methodology (GLEAM) for EF,
and radar precipitation from the
NEXt generation weather RADar system (NEXRAD)), FLUXNET station data, and the
North American Regional Reanalysis (NARR). Data sets agree
on a region of positive relationship between
EF and precipitation occurrence in the southwestern US. However, a region of
strong positive relationship over the eastern US in NARR cannot be
confirmed with observation-derived estimates (GLEAM, NEXRAD and FLUXNET).
The GLEAM–NEXRAD data set combination indicates a region of positive EF–precipitation
relationship in the central US.
These disagreements emphasize large uncertainties in the EF data.
Further analyses highlight that
much of these EF–precipitation relationships could be explained by precipitation
persistence alone, and it is unclear whether EF has an additional role in triggering
afternoon precipitation. This also highlights the difficulties in isolating
a land impact on precipitation. Regional analyses point to
contrasting mechanisms over different regions. Over the eastern US,
our analyses suggest that the EF–precipitation relationship
in NARR is either atmospherically controlled (from precipitation
persistence and potential evaporation) or driven by vegetation interception
rather than soil moisture. Although this aligns well with the high
forest cover and the wet regime of that region,
the role of interception evaporation is
likely overestimated because of low nighttime evaporation in NARR. Over the central and
southwestern US, the EF–precipitation relationship is
additionally linked to soil moisture variations, owing to the soil-moisture-limited climate regime. |
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