Day-to-day meteorological variability in northern Chile: impacts and predictability René D. Garreaud Department of Geophysics Universidad de Chile General.

Day-to-day meteorological variability in northern Chile:impacts and predictability

René D. GarreaudDepartment of Geophysics

Universidad de Chile

• General circulation and climate context• Regional circulation• Mid-latitude systems• Central Andes Convection• Weather forecasting: Basis – Methods - Applications

ZCITecuador

33SA

B

B

Circulación media de gran escala

B

In the context of weather and climate phenomenaatmosphere continuum fluid

gFpVkfdtVd

R

1ˆ

SfcConvRADPQQQSTV

t

)(

0p

V

pRT

pgz

)(

Basic equations

But ...

• Previous system is highly non-linear and implicit; no analytic solution can be obtained

• Some physical processes are difficult to model (cloud formation, radioactive transfer, surface exchange, etc.)

.... Numerical modeling

•Use regular grids (vertical coordinate)

•Finite differences in space and time (vs. Spectral models)

•Parameterization of sub-grid processes

Regional versus Global modeling

Regional Global

Horizontal domain 1000 1000 km2 108 km2

Horizontal grid spacing 5-50 km 200-500 km

Horizontal grid type Regular grid point Spectral (T45 / R63)

Vertical resolution below 800 hPa 10-15 4-9 (5 in CCM3)

Integration times Days to weeks (year?) Season to decades

Spin-up time Few hours Few years

Lead applications NWP –

Diagnosis of weather events Climate studies, seasonal

prediction

Physical parametrizations Several options Single option

Initialization (IC) Analysis Cold start

Lateral Boundary Conditions (LBC) Analysis, Forecast

Bottom Boundary Conditions (BBC) Fixed / Coupled Coupled with ocean

or land

Regional atmospheric modeling: Current status Regional atmospheric modeling is currently being performed in many groups at Universities, State Agencies and Private companies, in part because:

Availability of modestly priced single and multiprocessor workstations that provide "supercomputer" processing capabilities

Availability of regional (synoptic-mesoscale) models that run efficiently on workstations, sometimes as a black box (MM5, RAMS)

Real-time accessibility of analysis and forecast grids from operational, global models (MRF-NCEP, ETA-CPTEC, etc.)

a. Met. variable (Taire, R, etc.)

b.Seeing (T1 día)

c. River runoff (T1 semana)

d. Tomato growth (T2 mes)

Time (2 months)3 days

NowcastWeather forecast

Weather forecastExtended forecastInitial conditions

Climate predictionInitial conditions

Vis

IR (cercano)Vapor de Agua

IR(lejano)

MM5-DGF (2002)D1

D2

D3

Detalles de la corrida

D1: 135 x 135 (km) - 34 x 40 x 30 puntosD2: 45x45 (km) - 55 x 55 x 30 puntosD3: 15 x 15 (km) - 73 x 73 x 30 puntos

Inicialización: Un ciclo 0000 UTC (2000 HL) cada díaPeriodo de simulación: 72 horasIntervalo de salida: 1 horaCondiciones de borde e iniciales: NCEP-NOAA (USA)

met.dfg.uchile.cl/tiempo/MM5

Mapassinópticos

Seriesde Tiempo

Cortestiempo-altura