# Presentation: 742239

## Products expressed in terms of climate anomalies

- Yuejian Zhu and Zoltan Toth
- Environmental Modeling Center
- NCEP/NWS/NOAA
- December 13th  2005

## Input climate/forecast data -- current available

- NCEP/NCAR reanalysis data
- 4 cycles (00UTC, 06UTC, 12UTC and 18UTC) per day
- 40 years (Jan. 1st 1959 – Dec. 31th 1998)
- Need to consider the systematic difference between NCEP/NCAR reanalysis and current analysis (GDAS)
- Resolution and format
- 2.5*2.5 (lat/lon) grid, GRIB-1 format
- 1.0*1.0 (lat/lon) grid, GRIB-1 format (forecast only)
- Variables at levels (possible to add more)
- Height: 1000hPa, 700hPa, 500hPa, 250hPa
- Temperature: 2m, 850hPa, 500hPa, 250hPa
- Wind: 10m, 850hPa, 500hPa, 250hPa
- PRMSL, max/min temperature

## Climatological mean (estimation)

- To use Fourier expansion from 40 years data and compare following four considerations
- Considering first Fourier mode: a1 and b1
- Fits to daily data to obtain annual cycle
- Considering first two Fourier modes: a1,b1,a2 and b2
- Fits to daily data to obtain annual and semi-annual cycle
- Considering first three Fourier modes: a1,b1,a2,b2,a3 and b3
- Fits to daily data to obtain annual, semi-annual and 4-month cycle
- Considering first four Fourier modes: a1,b1,a2,b2,a3,b3,a4 and b4
- Fits to daily data to obtain annual, semi-annual, 4-month and seasonal cycle

## Higher moments (estimation)- work on the anomalies from mean

- Standard deviations:
- Based on 4 different daily means (previous slide)
- To get 40 years average daily standard deviation first
- To calculate monthly mean of standard deviation from daily
- To generate a slope from month to month
- To project to daily standard deviation from monthly mean

## Products (plan)

- Based on 4 different considerations (choose one)
- Assuming the normal distributions of the 40 years climate data
- PDF will be presented by first two moments (mean and standard deviation)
- Considering the systematic differences between NCEP/NCAR reanalysis and current GDAS
- Using bias corrected forecasts
- To calculate climate anomaly:
- For 1x1 degree grid point globally.
- For all 19 variables (height, temperature, wind and etc.)
- For each ensemble member.
- Output in percentile (0-100%, 50%=normal).

## Discussion

- How many modes we need to consider?
- In general, more modes will be better
- First two modes are enough for the heights
- Surface variables and winds are challenged
- Are all variables normal distribution?
- Depends on variables and geographical locations (?)
- Most of them are normal distribution
- Examples of 2-meter temperature and 10-meter u
- Monthly distribution of 500hPa height has a little seasonal tilt
- Examples of time series for daily mean and standard deviation for all 19 selected variables
- Two physical locations (near Washington DC and Ottawa)
- Are these plots enough to demonstrate?
- http://wwwt.emc.ncep.noaa.gov/gmb/yzhu/html/CLIMATE_ANOMALY.html

## Notes for presentation and posted maps

- Examples of future application for NAEFS
- Visit http://wwwt.emc.ncep.noaa.gov/gmb/yzhu/html/CLIMATE_ANOMALY.html
- For four different modes consideration (need choose one only)
- January 15th and July 15th are posted to contrast of seasonal difference
- 0000UTC and 1200UTC are posted to contrast of daily cycle
- November 8th 0000UTC 2005 raw forecasts are used as example
- Only one ensemble member is demonstrated
- Differences (reanalysis and GDAS) are not considered (not available yet)
- Bias corrected forecasts will be used when final application
- Anomaly forecast maps are shown normal (0%), above normal (+%) and below normal (-%) respectively
- Maximum and minimum temperatures
- Not quite right! 6 hours climate .vs 12 hours forecast (only available right now)
- 6 hours tmax and tmin will be generated soon for ensemble system.

## Mean (one mode)

- Mean (four modes)

- Mean (four modes)

- height

- temperature

## height

- temperature

## 10m U

- One mode

- Four modes

- Near DC

- Near Ottawa