Identification

Title

A comparison of the Diel cycle of modeled and measured latent heat flux during the warm season in a Colorado subalpine forest

Abstract

Precipitation changes the physiological characteristics of an ecosystem. Because land-surface models are often used to project changes in the hydrological cycle, modeling the effect of precipitation on the latent heat flux lambda E is an important aspect of land-surface models. Here we contrast conditionally sampled diel composites of the eddy-covariance fluxes from the Niwot Ridge Subalpine Forest AmeriFlux tower with the Community Land Model (CLM, version 4.5). With respect to measured lambda E during the warm season: for the day following above-average precipitation, lambda E was enhanced at midday by approximate to 40 W m(-2) (relative to dry conditions), and nocturnal lambda E increased from approximate to 10 W m(-2) in dry conditions to over 20 W m(-2) in wet conditions. With default settings, CLM4.5 did not successfully model these changes. By increasing the amount of time that rainwater was retained by the canopy/needles, CLM was able to match the observed midday increase in lambda E on a dry day following a wet day. Stable nighttime conditions were problematic for CLM4.5. Nocturnal CLM lambda E had only a small (approximate to 3 W m(-2)) increase during wet conditions, CLM nocturnal friction velocity u(*) was smaller than observed u(*), and CLM canopy air temperature was 2 degrees C less than those measured at the site. Using observed u(*) as input to CLM increased lambda E; however, this caused CLM lambda E to be increased during both wet and dry periods. We suggest that sloped topography and the ever-present drainage flow enhanced nocturnal u(*) and lambda E. Such phenomena would not be properly captured by topographically blind land-surface models, such as CLM.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7n300qg

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2018-03-01T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact