Local and urban scale modeling - Air Pollution Modeling and Its Application - page 6

References
Friedl, M.A., D.K. McIver, X.Y. Zhang, J.C.F. Hodges, A. Schnieder, A. Bacinni, A.H. Strahle r,
A. Cooper, F. Gao, C. Schaaf, W. Liu, 2001: Global land cover classification results from
MODIS. Geoscience and Remote Sensing Symposium, IGARSS apos; 01. IEEE 2001
International 2, pp.733-735.
Homer, C, Huang, C, Yang, L, Wylie, B. and Coan, M. 2004: Development of a 2001 National
Land-cover Database for the United States. Photogrammetric Engineering and Remote
Sensing , 70 :829-840.
Pleim, J. E., Xiu, A., Finkelstein, P. L., Otte, T. L., 2001. A coupled land-surface and dry
deposition model and comparison to field measurements of surface heat, moisture, and ozone
fluxes. Water, Air, & Soil Pollution: Focus 1, 243-252.
Xiu, A., and J.E. Pleim, 2001: Development of a Land Surface Model. Part I: Application in a
Mesoscale Meteorological Model. J. Appl. Meteor ., 40 , 192-209.
5. Questions and Answers
Question 1: How is the bi-directional ammonia surface flux modeled in relation to
land use?
Answer 1: Currently, the ammonia bi-directional model specifies the gamma
values (NH4 + /H + ) for soil and stomata according to land-use category such
that cropland uses gamma = 1,000 and all other vegetated LU categories use
gamma = 100. This is a prototype. We are developing methods to derive more
realistic gamma values from data on crop types and fertilizer application.
Question 2: Nowadays land use data is available on a very detailed scale, but it
depends on the algorithms used to extract information from the signal. Do we
know the accuracy of this procedure and how it has been tested?
Answer 2: Land use data is normally generated from satellite images with digital
signals based on classification algorithms, such as cluster algorithms. The 2001
National Land Cover Database (NLCD) has been developed under the Multi-
Resolution Land Characteristics (MRLC) Consortium which is a group of US
federal agencies. It is well documented database with detailed accuracy assess-
ments. 1992 NLCD land cover dataset was first developed in the early 1990s
from Landsat 5 TM images. 2001 NLCD data was developed in the recent
years mostly from Landsat 7 TM images. This new 30 m resolution land cover
data set is well documented and evaluated based on ground truth field infor-
mation by different agencies. The data set has been created from an improved
classification algorithm in comparison with the 1992 NLCD land cover data.
The technical methods and algorithms used to generate the 2001 NLCD data
set is published in a journal article.