Problems 1. Observation counts. Estimate the number of observations taken each day using information in Table 2.1. Assume the following. (i) One “observation” equals one scalar variable at one at one time. (ii) vector horizontal are 2 scalar variables. Each satellite wind is at only 1 level. (iii) where ranges are given in the table, use the larger value. (iv) a “report” in the table can include many “observations” as defined here. (v) assume only 10 “standard” levels are obtained from each radiosonde/rawinsonde sounding. Assume each satellite temperature sounding is 20 values. Show your estimates for each of the observing systems listed in the table separately, then indicate the “grand total”. 2. Rough economics of observing systems. Very roughly estimate the relative costs of sampling the atmosphere by radiosondes versus by satellites 4 times daily for 5 years. Assume that each geostationary weather satellite: costs 300 M Euros to build and put into orbit, takes 4000 soundings each day, and lasts for 5 years. Assume 5 satellites can cover most of the globe (high latitudes excluded). Assume that radiosondes could be dropped from 4000 drones flying at high altitude over the oceans and from 800 land stations. Assume that each radiosonde costs 20 Euros and each station and drone releases 4 each day. Assume that each drone costs 100,000 Euros to build and 100 Euros each day to maintain. Assume that a shipboard weather station costs 10M Euros to build and lasts 10 years, has minimal staff salaries of 300,000 Euros per year, and requires 500 Euros to operate each day. Each radiosonde balloon costs 100 Euros to launch and there are 4 releases per day. Assume that the costs of receiving the data are the same and neglect it for this calculation. Ignore the difference in vertical resolution of winds and moisture for the three systems. a. Estimate the total cost for 5 years of each system. b. Estimate the cost per observation for each system, assuming each sounding produces 20 observations. (temperature and wind only) ********** GOT TO HERE ************
Table 2.1 Properties of various operational observing systems. Error Observing system Fields observed Random error Remarks Time resolution Coverage Vertical resolution Horizontal resolution Comments and (reports/day) Surface land stations PS TS VS rhS ±0.5 mb ±1°C ±1.5 – 3 m/s ±10% – ≥ 3 locations). – ≥ 50 km high resolution over most land areas. 4,095 of 9,500 stations in WWW (20,000/day; in 1992) (27,500 metar/day; in 2000)
Rawinsonde & radiosonde Soundings T V ±0.5-2.°C ±3 m/s ±5 m/s > ±2°C in Stratosphere. below 500 mb. above 500 mb. 6–12 locations) ~50 mb ≥ 300 km (see Figure 2.1) 885 stations (1200 soundings/day). 5 ocean weather ships by 1990. By 2000, no more ships, ~670 stations. About 600 pibal stations (1000 soundings/day): wind only in 1990. By 2000, 74 stations rh ±5% Much larger for T<-40 oC Buoys, Ocean platforms (incl. oil rigs, etc.) PS TS VS ±1 mb ±1°C? ±? very few measure VS or air temperature 6–12 hours Originally mainly used of 20° S and . Later 500–1000 km 130–200 were operational during GWE. 300 (2500/da) plus ~170 (600/da) are moored in 1990. Only
coverage is global moored measure VS. By 2000: ~2,200 drifting and 915 moored. Merchant (1) Surface Only PS TS VS rhS ±0.5 mb ±1°C ±1.5–3 m/s ±10% assumed same as for surface land station ≥ 3 main shipping routes varies greatly About 7,400 ships (3500/da) in 1990. By 2000: 777 ships. Few ships in southern oceans (2) ASAP or other upper air T V rh ±1°C ±3 m/s ±10% assumed same as for radiosondes ≥ 12 main shipping routes ~50 mb varies greatly About 15 ships (30/da) equipped by 1989 Commercial Aircraft: (1) Post-flight reports V ±6 m/s less error for inertial navigation system (INS) continuous air routes 200–300 mb level only 500–1000 km (~100 reports per day) roughly 10 observations per report
(3) Vertical water vapor sounder TCPW Or WV or rh in layers 2-4 kg/m2 error std ? ±20– 30% large errors in clouds continuous global ~400 mb ~50 km (4) winds (CTW) V ±4.5–5.5 m/s for low level CTW ±9–10 m/s for high CTW In situ of winds suggest much smaller of 1–3 m/s continuous 55° N to 55°S 200–500 mb See Fig. 2.6 30–400 km (About 6,000/day in 1983). (7,000/day in 1990) (>45,000 per day by 2000) Most are over oceans. Speed bias m/s. Newer systems 1–7 m/s better than old. (5) Scatterometer VS ±0.5–2 m/s <17 degrees Rms errors continuous 25-50 km over ~600 km swath Ocean surface (~58,000 values/day)
Primary reference Kanamitsu et al. (2002) Uppala et al. (2005) Input Data Satellite data: NESDIS TOVS temperature retrievals, track winds. (No moisture data used) Direct assimilation of VTPR, TOVS (HIRS, MSU, SSU) and AMSU-A Level-1c radiances, Atmospheric Motion Vectors, scatterometer winds, SSM/I radiances as 1D-Var retrievals of TCWV and surface wind speed TOMS and SBUV data in ozone analysis, Altimeter wave height data (see Hernandez et al., 2004) air data Radiosondes, dropsondes, pibals, aircraft data, wind profilers Radiosondes, dropsondes, pibals, aircraft data, wind profilers Surface data (snow cover) Stations, ships, buoys, PAOBs, (NSIDC-based, USAF snow cover after fall 1998, depth is dynamic) Stations, ships, buoys, PAOBs. (SYNOP snow depth, most after 1976) SST and Sea Ice AMIP-II (should be same as ERA-40 except for time interpolation, Kanamitsu, pers. comm., 2007), Reynolds SST 1999 Reynolds et al. (2002), Rayner et al. (2003) and NCEP products Period 1979- present September 1957-August 2002 (45 years) Table 2.4 Some aspects of the NDRa2 and ERA-40 assimilation systems. Acronyms and abbreviations are defined in the appendix. From Grotjahn (2008) Dataset ERA-40 Primary reference Kanamitsu et al. (2002) Uppala et al. (2005) Period 1979- present September 1957-August 2002 (45 years) Assimilation model Model based on: MRF (ca 1995, with modifications) full radiation calculation hourly ECMWF forecast model CY23r4 (operational in June 2001) Assimilation scheme 3DVAR (Parrish and Derber, 1992) 3DVAR-FGAT, OI for surface parameters and ocean wave height