Partitioning the solar radiant fluxes in forest canopies in the presence of snow

Abstract

[1] The main goal of this study is to help bridge the gap between available remote sensing products and large-scale global climate models. We present results from the application of an inversion method conducted using both MODerate resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging SpectroRadiometer (MISR) derived broadband visible and near-infrared surface albedo products. This contribution is an extension of earlier efforts to optimally retrieve land surface fluxes and associated two-stream model parameters . It addresses complex geophysical scenarios involving snow occurrence in mid and high-latitude evergreen and deciduous forest canopy systems. The detection of snow during the winter and spring seasons is based on the MODIS snow product. This information is used by our package to adapt the prior values, specifically the maximum likelihood and width of the 2-D probability density functions (PDF) characterizing the background conditions of the forest floor. Our results (delivered as a Gaussian approximation of the PDFs of the retrieved model parameter values and radiant fluxes) illustrate the capability of the inversion package to retrieve meaningful land vegetation fluxes and associated model parameters during the year, despite the rather high temporal variability in the input products, in large part due to the occurrence of snow events. As a matter of fact, most of this temporal variability, as well as the small differences between the MODIS and MISR broadband albedos, appear to be largely captured by the albedo of the forest canopy background.

A Simple Method for Retrieving Understory NDVI in Sparse Needleleaf Forests in Alaska Using MODIS BRDF Data

“…NDVIu is calculated as the average of the regression NDVI values with the lowest bidirectional variability: (2) in which N is the number of solar-view angles used in regression analysis (N = 7 in this study).…”

“…It describes the vegetation canopy structure and can be related to the energy absorption capacity of vegetation [1]. To monitor LAI at a continental and/or global scale over long periods of multiple years, satellite remote sensing is currently the only feasible technique [2]. Over the last decades, several scientific teams (e.g., [3][4][5]) have provided several global LAI products.…”

Consistent retrieval of land surface radiation products from EO, including traceable uncertainty estimates

“…For example, Pinty et al (2007) analyse differences between JRC-TIP products derived from MODIS and MISR broadband WSAs. Pinty et al (2008) apply the same strategy but to high-and midlatitude sites, as their focus lies on the behaviour of JRC-TIP products in the presence of snow. MISR is an instrument flying on the same platform (called Terra) as one of the MODIS instruments, and the procedure for deriving a WSA comparable to the standard MODIS product is described by Pinty et al (2007).…”

“…Accordingly, the system is typically operated on albedo input in these two wavebands. In this configuration it has been applied to broadband albedos derived from MODIS (Pinty et al, , 2008(Pinty et al, , 2011a, MISR (Pinty et al, , 2008, and GlobAlbedo (Disney et al, 2016). Section 4 describes enhancements of robustness and efficiency through the use of so-called TIP tables, i.e.…”

“…The Joint Research Centre Two-stream Inversion Package (JRC-TIP; Pinty et al, 2007Pinty et al, , 2008) is a retrieval package that fulfils the conditions above. It is built around a twostream model of the RT in the canopysoil system (see Sect.…”