# Presentation: 916948

## Sweden

**of operational **
**Numerical Weather Prediction**
**in **
**Sweden**

## Why Sweden?

**-C. G. Rossby back from the US 1947**
**(home-longing, management and politics)**
**-Swedish state-of-art computers****	**
**(BARK 1950, BESK 1953)**
**-International support**
**(from the USA and Belgium)**

## 1953 BESK=

**1953 ****BESK=**
**Binary **
**Electronic**
**Sequence  Calculator**

## BESK 

**BESK**** **
**In 1953 the world’s “best” computer**

- Electrostatic drum memory

- “Williams tube” memory

- Control desk

- Arithmetic unit

## The International Meteorological Institute

- Rossby wanted, like V. Bjerknes after WWI, to play an international role in the political reconstruction after WWII

- Eady

- V. Mieghem

- Rossby

- Steyer

- Hubert

- Vuorela

## Baroclinic or barotropic models?

**...****yes, but the **
**large scale motion **
**can kinematically **
**be described by a **
***barotropic***** model**

**The atmospheric **
**motions are **
**driven by **
**thermal processes **
**as reflected in **
***baroclinic ***
**developments**

**R. C. Sutcliffe**

**C. G. Rossby**

## Common misinterpretations of

** ****Rossby’s barotropic concept**
**-Only valid for stationary waves**
**-Can only perform linear extrapolations**
**-Only valid for barotropic features**
**-Group velocity....**

## The concept of group velocity tells us that any boundaries have to be placed far enough away 

**from the verification **
**region**

- 24-hour compu-
- tational areas for
**- MISU**
**- UKMO**

## A +24 hour forecast from the UKMO system winter 1953-54

**A +24 hour forecast from the UKMO system winter 1953-54**

- Boundary
- errors and
- numerical
- instability

## Only in 1965 did the UKMO go operational with NWP after

- a personal intervention by the new Director General John Mason

**Oh dear...**

**Dear members of the**
**press, radio and TV...**

## In Stockholm tendency calculations were carried out, first by hand in 1952, later on BESK in 1953

**The Swedish tabloid *****“Expressen”***** published the results almost a year before *****“Tellus” *****(forecast left, analysis right)**

## +24 h baro-

**+24 h baro-**
**tropic forecast**

**3 January 1954 00 UTC**

**2 January**
**1954 00 UTC**

**Barotropic re-run of the “tree-feller” **
**storm the 2-3 January 1954 **

## First real time NWP in late September 1954

- Not quite the 72 hour computational area

- 72 hour verification area

## From the operational period Dec 1954-May 1955

**-Professor **
**Dahlqvist,**
**when is **
**Spring coming?**

**From the operational period Dec 1954-May 1955**

## -Tomorrow at 2 pm!

**-Tomorrow at 2 pm!**

**+72 hours**

## ...and Spring came!

***...******and Spring came!***

## Why Sweden succeeded:

**-C. G. Rossby back from the USA 1947**
**-Swedish state-of-art computers **
**-International support **
**-Choice of barotropic model**** (skilful and providing operational experience)**
**-Efficient automatic analysis system**** (Bergthorsson-Döös, 1955)**
**-Not too small NWP area ****(but not too big either, avoiding retrogression of the planetary waves!)**

## From wheat to bread! 

- Bert Bolin shows automated 500 mb forecasts for Ragnar Fjørtoft (Norway) and George Corby (UK) around 1956