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Analyses & Numerical Prediction Analysis and Prediction Operations Bulletin No. 39
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A new mesoscale prognosis system, developed by the Regional Meteorology Group, led by Dr.Kamal Puri in BMRC, is to be introduced into operations at the NMC Melbourne. This new system, which has the acronym MESO_LAPS (standing for "MESO scale Limited Area Prediction System") is basically a higher horizontal resolution (0.250 latitude/longitude) configuration of the prognostic component in LAPS. No assimilation, or analysis, of new or extra data types is performed, at this stage. However, one new feature is the incorporation of a daily soil moisture analysis, developed by Neil Pescod, into the system. Enhancements to the Diagnostic Processor were made by Tan Le of BMRC.
In its operational mode, MESO_LAPS will run over two domains - one for South East and one for South West Australia. Forecasts out to 36 hours will be produced, for each domain - twice a day, from 00 and 12 UTC, after the completion of LAPS. Products from the system will be available through the real time data base ('rtdb'), DIFACS, MCIDAS and the internal web (the latter being accessible from the regions).
A simplified view of the operational structure of MESO_LAPS is shown in Figure 1. LAPS - the operational limited area system covering the full Australian region domain - provides the basic starting analysis (an interpolated version) and also the lateral boundary conditions. (During nesting, absolute values of the mean sea level pressure, wind components, temperatures and mixing ratios, from LAPS, are used at 3 hourly intervals.) The Pre-processor collects 'windowed' versions of the LAPS and climatological data (which, at this stage, includes the NMC weekly SST and the daily soil moisture analyses), and prepares a preliminary starting analysis and boundary conditions in the same file format. In the mass flux module, mass flows at the lateral boundaries are balanced by adjusting the winds.
As noted in APOB No.36, the prognosis component is a hydrostatic primitive equation model including a wide range of physical processes (viz., deep, mid-level and shallow convection (through a mass flux scheme), broad scale rain, radiative transfer with a diurnal cycle, diagnostic clouds, stability dependent surface fluxes and interactive soil moisture). For MESO_LAPS, the model has been configured to produce forecasts out to 36 hours on a 0.250, 120x160, latitude/longitude grid with 19 vertical -levels for two domains.
| (i) | Domains: | ||||||||
| South East Australian: | 22.250 S-52.00S, 125.00E-164.750E | ||||||||
| South West Australian: | 15.250 S-45.00S, 95.00E-134.750E | ||||||||
| (ii) | Horizontal resolution: | 0.250 (120x160 latitude/longitude grid) | |||||||
| Figures 2 and 3 show the two domains and associated grid points.
FIGURE 2 South East Australian Grid.
FIGURE 3 South West Australian Grid. |
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| (iii) | Vertical resolution: | No. of sigma levels=19 | |||||||
| Levels=0.991, 0.975, 0.950, 0.900, 0.850, 0.800, 0.750, 0.700, 0.600, 0.500, 0.400,
0.350, 0.300, 0.250, 0.200, 0.150, 0.100, 0.070, 0.050 The vertical resolution and the distribution of levels is identical with that of LAPS. |
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| (iv) | Topography: | See Figures 4 and 5. | |||||||
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FIGURE 4 South East Australian Topography.
FIGURE 5 South West Australian Topography. |
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| (v) | Initialisation: | digital filtering technique | |||||||
| (vi) | Timestep: | 30 seconds | |||||||
| (vii) | Nesting: | lateral boundary conditions derived from +3 to +36 hour LAPS forecasts | |||||||
| (viii) | Output: | Starting analysis and forecasts to 36 hours from 00 UTC and 12 UTC daily | |||||||
| (ix) | Climatology: | albedo. | |||||||
| (x) | Soil moisture Analysis: | Daily 0.250x0.250 | |||||||
| (xi) | Sea Surface Temperature Analysis: | Weekly 10x10 O.I. (NMC Melbourne) | |||||||
| (xii) | Cray YMP resources: | ||||||||
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| (xiii) | NMC applications driven by MESO_LAPS: |
Eventually the Bass Strait seastate model (WAM) will be driven by the 10 m
boundary layer winds derived from MESO_LAPS.
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| (xiv) | Backup: | At the present time, there is no backup system. On days when preventative maintenance occurs on the Cray YMP (the first Tuesday in every month), a full set of products may not be available. | |||||||
T.Skinner (MSDSS,NMC) has undertaken a synoptic assessment of MESO_LAPS. Some preliminary results, based on the products for April, have shown the following characteristics:
Ongoing assessments will appear in the NMC Quarterly Summary.
Charts from MESO_LAPS are found in the DIFACS slots: 864-892. Two sample charts from DIFACS are shown in Figures 6 and 7.
FIGURE 6a 36 hour prognosis for South East Australia
--- Mean Sea Level Pressure.
FIGURE 6b 36 hour prognosis for South East Australia
--- Precipitation.
FIGURE 7a 12 hour sigma level (0.991) wind prognosis
for South West Australia.
FIGURE 7b 12 hour sigma level (0.975) wind prognosis
for South West Australia.
Only the latest LAPS charts will be displayed on Difacs.
A limited set of sigma and pressure level output from MESO_LAPS is written to the real time data base (rtdb). The initial condition and forecast fields (out to +36 hours, in 3 hourly intervals), on a 120x160 grid, are available for the South East and South West Australian domains. The data base currently holds MESO_LAPS fields for the last 10 days.
MESO_LAPS fields are available through MCIDAS. For regional users, the fields will only be available by using the ADDE facility (with MCIDAS V7) with the commands: GRDLIST and GRDDISP. For Head Office users, the relevant grids are as follows:
GRID1700,...,GRID1712 (SE pressure level data)
GRID1715,...,GRID1727 (SE sigma level data)
GRID1730,...,GRID1742 (SW pressure level data)
GRID1745,...,GRID1757 (SW sigma level data)
The GRIDs contain 3 hourly fields out to 36 hours.
It is noted that some specialised products from MESO_LAPS are currently available through the internal web server.
Other products associated with MESO_LAPS (eg HYSPLIT trajectories) will be made available through this mechanism, over the next few months.
At the present time, no archiving of products on magnetic cartidges will occur.
It is planned to set up another configuration of MESO_LAPS so that the operational staff in NMC will have the ability to define an arbitrary domain, covering an area of meteorological significance, and then run the system. The operational system will be further developed to incorporate its own analysis, or assimilation, making use of new data types. Ongoing improvements in the model (eg a new PBL scheme, and semi-Lagrangian and non-hysdrostatic formulations) are to be expected. It is also planned that other systems, like the HYSPLIT air dispersion model, will be connected to MESO_LAPS.
"The new BMRC Limited Area Prediction System (LAPS)." K.Puri, G.Dietachmayer, G.Mills, N.Davidson, R.Bowen and L.Logan. To appear in Australian Meteorological Magazine 1997.
"A Four-parameter, Three-layer Model of Soil Moisture Based on Hydraulic Properties of the Soil in the Absence of Vegetation." N.R.Pescod. BMRC Research Report No.46, pp.101-106, 1994.
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