Surface Energy Budget Components Research Articles

A method to derive downwelling longwave fluxes at the Arctic surface from TIROS operational vertical sounder data

The dominant component of the polar surface energy budget during half the year is the downwelling flux of longwave radiation (DLF), yet little is known about its spatial and temporal variability except on monthly timescales. As surface measurements will always be sparse, the most promising opportunity for diagnosing the DLF is provided by satellite data. Estimating this flux from space, however, presents challenges over all surface types and particularly in polar environments where cloud detection and cloud fraction estimation are less certain. A new method is presented to estimate DLF from measurements by the TIROS‐N operational vertical sounder (TOVS). Temperature profiles, humidity estimates, and cloud cover are retrieved from TOVS radiances using the improved initialization inversion algorithm, which has been modified to produce more accurate results over snow and sea ice. This information is combined with brightness temperature differences from pairs of infrared and near‐infrared TOVS channels. These differences are used to infer cloud phase and geometric thickness. Longwave fluxes are then calculated using a forward radiative transfer model. Results during winter 1988 and spring 1992 are compared with hourly radiation measurements from the Coordinated Eastern Arctic Experiment in the eastern Arctic basin and from the Lead Experiment in the Beaufort Sea. Error analyses yield a bias of approximately 3 W m−2, a standard deviation of 23 W m−2, and a correlation coefficient of about 0.75. These errors are comparable to results from similar studies over midlatitude land and ocean areas where clouds are more easily identified.

Calculation of the global land surface energy, water and CO2 fluxes with an off‐line version of SiB2

Global land surface fluxes of energy and CO2 have been simulated using an off‐line version of a biosphere‐atmosphere model, SiB2, forced with analyzed or observed atmospheric boundary layer mean potential temperature, water vapor mixing ratio, and wind, surface downward solar and thermal radiation, and precipitation. The off‐line model is called SiBDRV. Soil and vegetation boundary conditions were specified from satellite data and other sources. The European Centre for Medium‐Range Weather Forecasts (ECMWF) data assimilation system products were used to derive the atmospheric and radiative forcings. Precipitation was based on station observations. The SiBDRV results were compared with corresponding simulation results produced by the Colorado State University general circulation model (CSU GCM), with the ECMWF assimilation system output and with observations. Differences between the surface energy budget components and the surface climatology produced by SiBDRV and the ECMWF assimilation system are due to differences in the land surface parameterizations between the two models. SiBDRV produced lower surface latent heat fluxes and larger sensible heat fluxes than the ECMWF data assimilation, partly due to large canopy resistent term explicitly formulated by SiB2 and possible precipitation differences between the SiBDRV precipitation forcing and the ECMWF data. Differences between the SiBDRV and the CSU GCM results are due to the different climates associated with the ECMWF assimilation system output, which is strongly constrained by assimilated observations, and by the CSU GCM, which is run in pure simulation mode. More specifically, the major reasons for the surface energy and CO2 budget differences between the SiBDRV and the GCM are greater incoming solar radiation in the GCM and differences in the precipitation patterns. The simulated global annual carbon uptake by the terrestrial biosphere is similar in SiBDRV and the GCM. The annual gross primary productions of SiBDRV (116 Gt) and the GCM (113 Gt) agree well with other studies, using either ecological process models or empirical regression models. SiBDRV takes up 10 and 5% more CO2 than the GCM in January and July, respectively. The seasonally varying land surface CO2 fluxes estimated by the SiBDRV and the GCM both compare reasonably well with the results of other calculations.

Modeling the clear‐sky surface energy budget during FIFE 1987

A canopy level soil‐vegetation‐atmosphere transfer model (land ecosystem‐atmosphere feedback (LEAF) model is used to simulate components of the daily surface energy budget. The Sellers et al. (1992b) model is used to relate unstressed canopy conductance to the fraction of the incident photosynthetically active radiation absorbed by the canopy and the simple ratio vegetation index. The multivariate randomized block permutation (MRBP) procedure is used to obtain values for a number of parameters used in environmental stress functions and the aerodynamic resistances. It is shown that the MRBP procedure was able to improve the LEAF model predictions for three responses (i.e., net radiation, sensible, and latent heat fluxes). When comparing model predictions to the observations for the four intensive field campaigns of the First International Satellite Land Surface Climatology Project Field Experiment, the model performance is reasonably good. The difference in the parameterization of canopy conductance between the Sellers et al. (1992b) model and the LEAF model is discussed.

Simulation of daily energy budget and mean soil temperatures at an arid site

Soil temperature is often inadequately based upon relatively few measurements at widely dispersed locations. Within arid regions, such as the desert southwestern United States, soils, microclimates, and thus soil temperature may be markedly heterogeneous. Because extensive measurement of soil temperature is often not feasible, models are needed that simulate soil temperature based on readily available soil survey and “above-ground” weather information. This paper describes a simple energy-budget based model for simulating daily mean temperatures within a bare arid land soil. The model requires basic information on soil physical properties, and daily weather data including air temperature, windspeed, rainfall, and solar radiation to calculate daily surface energy budget components and surface temperature. One of two alternative numerical methods is then used to calculated subsurface temperatures. Tests of the model using 1987 daily temperature data from an arid site at Yuma, Arizona resulted in root mean square deviations within 1.4°C between daily modeled and measured temperatures at both 0.05 and 0.10 m depths. Sensitivity analysis showed modeled temperatures at 0.05 m depth to be most sensitive to parameters affecting the surface energy balance such as air temperature and solar radiation. Modeled temperatures at 1.0m depth were relatively more sensitive to initial temperature conditions and to parameters affecting distribution of energy within the profile such as thermal conductivity.

Comments on ‘the relative effect of solar altitude on surface temperatures and energy budget components on two contrasting landscapes’

Comments on ‘the relative effect of solar altitude on surface temperatures and energy budget components on two contrasting landscapes’

The relative effect of solar altitude on surface temperatures and energy budget components on two contrasting landscapes

A solar radiation attenuation model has been combined with a steady-state surface energy budget model. The combined model was programmed to investigate the resultant surface temperatures and associated, causal energy budget components to changes in solar altitudes and air temperatures. Two contrasting landscape scenarios were investigated: a barren and a grassy plain, under cloudless skies. Solutions to these many computations are presented in graphical form in order to gain an improved perspective of the varied responses of changing surface temperatures and energy budgets as complex functions of different solar angles and air temperature regimes. The grassy landscape was much more conservative in its reaction to the forcing by these two environmental parameters. It is believed that the portrayed trends encompass the possible extremes encountered in a continuum of landscapes in the real world.

University of Colorado 1975 Field Season on Baffin Island

Eight individual research programmes were carried out by graduate students and one faculty member of the University's Institute of Arctic and Alpine Research (INSTAAR) during the 1975 field season. They were concentrated around the settlements of Broughton Island and Pangnirtung as well as the DEW line station at Cape Dyer. Field operations were facilitated by an early break-up, which permitted sea travel by canoe. ... Two investigations were carried out from ... [Pangnirtung]. The first concerned the Holocene climate of the area. ... The other study involved the surveying of ten moraine systems fronting individual cirque glaciers. The volume of the ice core and surficial and englacial till was measured. The figures obtained will be used in a study of contemporaneous rates of glacial erosion in these subpolar glaciers. The first of two research projects based around Cape Dyer was a study of the Quaternary geology of the area between Sunneshine and Monneshine Fiords. ... The second programme involved a study of the elevational limits of various types of "lichen-free" areas, varying from trimlines around glaciers to extensive areas on plateaus that were once mantled by a permanent or semi-permanent snow cover. Dating of the onset and disappearance of snow cover was carried out by lichenometry, and samples of dead vegetation (Salix) were collected for radiocarbon dating. Field programmes in Quaternary geology, plant ecology and palynology, limnology and fast-ice studies were carried out. ... Studies of water temperature and other standard measurements were carried out at several lakes. Planktonic hauls were made, and a study performed, on the effect of light on plankton levels. Field measurements on surface energy budget components were completed. They were designed to assist in improvising INSTAAR's fast ice melt-stage model. The local measurements at Broughton Island were supplemented by several flights in the Canadian Ice Reconnaissance Patrol over Davis Strait.