High-Resolution Land Use Data in WPS/WRF for Urban Regions Michael Duda MMM Division, NCAR Boulder, Colorado, USA Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University

Motivation With the latest release, version 2.2, of the WRF model in December 2006, two new components can be used in simulations over urban areas 1) The WRF Preprocessing System (WPS) is a new software package to replace the previous preprocessor - WPS includes capabilities for mapping high- resolution data sets onto model domains 2) The Urban Canopy Model (UCM) is now a standard component in WRF Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 1

Outline I. Background II. Urban Canopy Model III. WRF Preprocessing System IV. Mapping Land Use Data with WPS V. UCM+Urban Landuse Impact VI. Summary and Conclusions Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 2

Background - UCM Consider two ways to model urban effects Vary the soil constants (e.g. heat capacity and thermal conductivity) and parameters (e.g. surface albedo, roughness length and moisture availability) in atmospheric model Couple an Urban canopy model-layer model with atmospheric model Latter approach has many advantages, so UCM was added as a component for WRF in v2.2 Couple Noah LSM in WRF with a single layer urban-canopy model (UCM), based on Kusaka et al, 2001 Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 3

Background - WPS In WRF v2.2, the WPS replaces the previous preprocessor, the WRF SI The WPS contains several new features that allow for flexibility in creating initial fields Ability to ingest arbitrary gridded fields (after encoding them in the correct file format) Ability to combine different data sets of differing resolutions and projections E.g., USGS land use field and high-resolution urban land use Fine-grained control over how individual fields are interpolated Masked fields benefit in particular from this! Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 4

Components of the WPS geogrid : Defines simulation grids and horizontally static fields Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 5

Components of the WPS ungrib : Extract meteorological and time- varying surface fields from GRIB files Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 6

Components of the WPS metgrid : Horizontally interpolates time-varying fields to simulation grids Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 7

Components of the WPS High-resolution gridded urban data are provided here Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 8

The WRF Preprocessing System High-resolution urban data are given in separate files: Default global 24-category USGS land use data set (30-sec. resolution) High-resolution urban land use data set Advantage: High-res data do not need to be re-projected or subsampled onto global data set Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 9

The WRF Preprocessing System How are land use categories transferred to simulation grid? Model grid cell For a model grid cell, we consider all source grid cells that are >50% in that grid cell - we want the dominant, or most common, category among all source grid cells within model grid cell Land use category data Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 10

The WRF Preprocessing System How are land use categories transferred to simulation grid? Example: 12 – category 31 9 – category 32 5 – category 33 Thus, this model grid cell will receive urban land use category 31 Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 11

The WRF Preprocessing System What about combining default and high- resolution urban data? Suppose the high-resolution data set is regional Step 1: Map regional data set categories onto model grid as before - here, we must respect areas with null values Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 12

The WRF Preprocessing System What about combining default and high- resolution urban data? After mapping high-resolution, regional data set to model domain, some model grid cells still have not been assigned a category Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 13

The WRF Preprocessing System What about combining default and high- resolution urban data? Step 2: Map global (or larger regional) data set onto only those points that have not already been assigned a cateogry! NB : This procedure can be applied repetitively for an arbitrary number of data sets Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 14

The WRF Preprocessing System Important points regarding WPS interpolation of high-resolution urban data sets: 1) Within interior of high-resolution data set, interpolation is “correct” regardless of relative resolution of source data 2) Near edges of data set, the extent of urban areas may be exaggerated when (resolution of data) > (resolution of model) Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 15

The WRF Preprocessing System The problem of over-extension of urban areas: High-resolution urban data set shown on top of coarse model grid; unshaded cells are assigned “missing value” flag Model grid cells receiving an urban category; note that a model grid cell is urban if it contains at least ½ of an urban source cell Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 16

Impact of High-Res Urban Categories WRFV2.2/UCM Runs: 18 hr simulations starting 25 Aug 2000, 12Z 4-domain nested run (27,9,3,1km) using AWIP data WRF (using USGS landuse with 1 urban category) WRF (using USGS landuse + high resolution urban land use data) WRF-UCM (using USGS landuse + high resolution urban land use data) Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 17

Impact of High-Res Urban Categories Domain configuration Domain 1 (27-km resolution): 85 x 68 Domain 2 ( 9-km resolution) : 145 x 106 Domain 3 ( 3-km resolution) : 190 x 160 Domain 4 ( 1-km resolution) : 199 x154 Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 18

Test Case: Houston Land use modifications for Houston based on high-resolution data New categories: 31 – Low-intensity residential 32 – High-intensity residential 33 – Commercial/Industrial Area of Houston data tile in relation to model domain; white=missing data and blue=valid data Urban areas (black) using USGS 24-category data set Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 19

Test Case: Houston Land use modifications for Houston based on high-resolution data Urban areas (black) using USGS 24-category data set Augmented urban areas (red shades) using new LU data set Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 20

Impact on 2-m Temperature of High Resolution Landuse over Houston Region WRF with high resolution LU WRF without high resolution LU Local Time: 9pm Local Time: Midnight Using high-resolution data produces more detailed distribution over the different urban categories and warmer 2-m T at night time over urban regions

Impact on Sensible Heat Flux of High Resolution Landuse over Houston Region Local Time: Midnight Local Time: 9pm Using high-resolution data produces more detailed distribution over the different urban categories and produces higher SHF at night time

2m-Temperature (UCM versus WRF) Local Time: 9pm Local Time: Midnight UCM produces 1-1.5 C higher temperatures as compared with WRF over urban regions and is more detailed

Sensible Heat Flux (W/m2) (UCM versus WRF) Local Time: Midnight Local Time: 9pm UCM produces 30-40 W/m2 higher night time flux as compared to WRF over urban regions

Summary and Conclusions In WRF V2.2, UCM is a standard component for use with Noah LSM The new capability of urban canopy modeling Provides detailed distribution of urban heat island Enhances mesoscale model forecasted wind and thermal structure over urban area Specification of urban landuse is critical High-resolution urban land use data sets are easily processed with WPS Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 25

Summary and Conclusions The data mapping capability of WPS can handle arbitrary gridded fields, not just land use Additional fields can be mapped to WRF domain as required by new urban model development For urban land use data sets, any number of categories may be mapped If model can make use of more specific categories, these can be handled in WPS Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 26

Questions? Third workshop on the Asian urban heat island issues 2006 February 28, Meisei University 27