Fei Chen and Jimy Dudhia April 2001 (Monthly Weather Review) 報告：陳心穎 Coupling an Advanced Land Surface-hydrology Model with the Penn State-NCAR MM5 Modeling System. PartⅡ:Preliminary Model Validation Fei Chen and Jimy Dudhia April 2001 (Monthly Weather Review) 報告：陳心穎

Introduction 在此文章，我們藉由合併模式的模擬和觀測資料的比較， 來評定合併模式MM5－New LSM。 為了比較是否有所改善，所以跟MM5－Slab Model及觀測 值作比較。 觀測資料是使用First International Satellite Land Surface Climatology Project(ISLSCP) Field Experiments (FIFE)，這 個密集資料是用來確認大尺度及中尺度模式的模擬結果。

a.FIFE observations b.NCEP 4-km national precipitation analysis Validation data a.FIFE observations b.NCEP 4-km national precipitation analysis

FIFE observation The data were collected over the Konza prairie in Kansas during the FIFE experiment (Sellers et al.1992) 1987 FIFE data used in this study are 1.area-average observations( ) 2.30-min averages at about 10 stations 3.include wind,air temperature and humidity,precipitation,incoming and reflected solar radiation,net radiation and incoming longwave radiation,a radiometric measure of the ground surface temperature,and soil temperature at 10 and 50 cm below the surface .

The dataset also includes the spatial-mean surface sensible heat ,latent heat,and ground heat fluxes averaged over 17 selected surface flux stations . The upper-air temperature and humidity data were from the visual tracked radiosondes. (Sugita and Brutsaert 1990)

NCEP 4-km national precipitation analysis A prototype,real-time,hourly,multisensor National Precipitation Analysis has been developed at the National Center for Environmental Prediction(NCEP)in cooperation with the Office of Hydrology (OH). Approximately 3000 automated,hourly digital raingauge observations .(48 states) 2. Hourly digital precipitation (HDP)radar estimates are obtain via the Automation of Field Operations and Services network.

Model configuration

Two sets of numerical experiments were conducted for several cases for 1987 and 1997 Four control simulations were designed for the 1987 case in order to verify the model against the FIFE observations. 1. 0000 UTC 4 June－0000 UTC 6 June (a clear sky day) 2. 0000 UTC 24 June－0000 UTC 26 June (a convective rain case) 3. 0000 UTC 9 August－0000 UTC 11August (a cloudy day) 4. 0000 UTC 12 August－0000 UTC 14 August (a large-scale rainfall case) The data from the NCEP-NCAR reanalyses

Two 48-h MM5 simulations were conducted for the 1997 case 0000 UTC 24 June－0000 UTC 26 June 0000 UTC 4 July－0000 UTC 6 July (both having large-scale frontal precipitation) The data from the NCEP EDAS (Eta Model Data Assimilation System analyses) This simulations used 23 vertical levels (with the model top at 100 mb). Three horizontal domains nested with two-way interaction with grid sizes of 90,30,and 10 km. inner domain is centered on the FIFE site in Kansas (for 1987 simulations). the ARM South Great Plains site in Oklahoma(for 1997 simulations)

Slab model 1.there is no explicit representation of vegetation effects. 2.the soil moisture remains constant during a simulation. 3.the soil moisture is defined in term of a moisture availability that depends on land use type.

Comparison results and discussions 1.validation of model surface heat fluxes 2.Evolution of temperature and humidity in the boundary layer 3.influence of the treatment of land surface processes on precipitation

Validation of model surface heat fluxes 1987 4 June－6 June(a clear sky day) 1987 12 August－14 August (precipitation)

1987 4 June－6 June(a clear sky day) Solar downward radiation 因為MM5中radiation scheme 沒有作aerosol的處理 Surface radiation forcing 夜晚有很好的長波輻射量估計

1987 4 June－6 June(a clear sky day) Latent heat flux 因為slab沒有複雜的植物物 理及蒸發散過程的交互作用 New LSM有明顯改善 100 W m-2 Sensible heat flux 初夏有很大的蒸發量，所以會 高估，但也比slab有改善 取得較好的Bowen ratio

1987 4 June－6 June(a clear sky day) 因為可感熱通量的高估，所以地表熱通量會較早到達最大值，也 可能是因為土壤溫度轉換到大氣邊界循環延遲。 地表能量平衡是不保守的，而模式是保守的，而地表溫度是由地 表能量平衡算出來的。 較暖 Ground heat flux Surface skin temperature

1987 4 June－6 June(a clear sky day)

1987 4 June－6 June(a clear sky day) 雖然在地表溫度有偏高，但是2-M溫度卻有較好的估計。(上午) 下午－晚間的溫度下降有延遲。 因為New-LSM有露的過程及正確的蒸發量，所以有呈現白天溼度 上升，晚上溼度下降的主要特徵 2-M air temperature 2-M mixing ratio

1987 12 August－14 August (precipitation) Solar downward radiation 第一天因為spinup(沒有雲) ，或沒有模擬出雨量 所以高估，第二天因為雨量 太多，所以低估。 Surface radiation forcing

1987 12 August－14 August (precipitation) Latent heat flux 因為第一天沒有模擬出雨量 ，所以高估。 Sensible heat flux

1987 12 August－14 August (precipitation) 因為第二天潛熱通量和可感熱通量的低估，所以兩圖白天都有 下降的趨勢 New LSM 有改善 2-M temperature 2-M mixing ratio

1987 12 August－14 August (precipitation) 第一天沒有模擬出雨量，第二天雨量過多 第一天土壤水分下降是因為吸收到根部區，第二天增 加到接近田間含水量(第一層)，所以流到第二層。 1st layer 2nd layer 3rd layer 接近田間含水量 Precipitation volumetric soil moisture in new LSM

Evolution of temperature and humidity in the boundary layer

Potential temperature 4 June 1987 1200 UTC 1530 UTC Mixing layer Potential temperature slab因為過多的可感熱，所以較暖 2330 UTC 1830 UTC

5 June 1987 1200 UTC 1530 UTC Potential temperature 2330 UTC 1830 UTC

5 June 1987 between 24－48-h and 0－24-h simulation 1200 UTC 1530 UTC Potential temperature 2330 UTC 1830 UTC

4 June 1987 1200 UTC 1530 UTC Mixing ratio 2330 UTC 1830 UTC

5 June 1987 1200 UTC 1530 UTC Mixing ratio 2330 UTC 1830 UTC

4 June 1987 ( increase 0.1 in initial soil temperature) 1200 UTC 1530 UTC Potential temperature 2330 UTC 1830 UTC

4 June 1987 ( increase 0.1 in initial soil temperature) 1200 UTC 1530 UTC Mixing ratio 2330 UTC 1830 UTC

Influence of the treatment of land surface processes on precipitation 1)Rain case of 24 June 1997 2)Rain case of 4 July 1997

1)Rain case of 24 June 1997 From 0000－1200 UTC 24 June 1997 NEXRAD analysis New LSM Slab

1)Rain case of 24 June 1997 From 0000－1200 UTC 25 June 1997 NEXRAD analysis Slab New LSM

2)Rain case of 4 July 1997 From 0000－1200 UTC 4 July 1997 NEXRAD analysis Slab New LSM

2)Rain case of 4 July 1997 From 0000－0300 UTC 5 July 1997 NEXRAD analysis Slab New LSM

Summary 在晴朗的天氣， 1. 太陽輻射的高估可能是因為MM5模式中的輻射方法沒有對 懸浮微粒的處理。 2. 新的LSM有取得正確的Bowen ratio。 3. 因為MM5-LSM有較精確的地表熱通量，所以在近地表的 溫度和溼度也比較接近觀測值。 4.在MM5-LSM和MM5-Slab都使用非局部的MRF PBL 參數化方法， 估計白天對流邊界層的溫度和溼度的發展，由於小尺度的異 質效應或大尺度平流，使得MM5模擬失敗。 在豪雨的天氣， 1. 模式在18h的模擬中，雲出現的太少、太慢，導致太多的 地表輻射量，所以地表熱通量也多。第二天相反。