# Presentation: 623249

## Comparative Influence of Snow and SST Variability on Extratropical Climate in Northern Winter 

**Fanglin Yang**
**RSIS/CPC_NCEP**
** **
**Arun Kumar**** **
**CPC/NCEP**
**NOAA’s 27th Climate Diagnostics and Prediction Workshop  ****, October  2002**

## Motivitations

**Compared to remote tropical SST forcing, how important is local snow anomaly in modulating mid-latitude climate variability?**

**In mid-latitudes,  air-sea interaction is one way.  Is snow-air interaction also one-way?**

**In extreme cases, for instance, in ENSO years, how snow and local temperature anomalies interact with each other? **

## GCM Experiments (NCEP GSM T42L28)

|  | SST
Specification  | Snow
Specification  | #
Runs  | Period of
Integration  |
| --- | --- | --- | --- | --- |
| SST_SNO  | Observed | Predicted | 3 | 1950-1999  |
| SST_CSNO  | Observed | Climatology | 3 | 1950-1999  |
| CSST_SNO  | Climatology | predicted | 1 | 150 years |
| CSST_CSNO  | Climatology | Climatology | 1 | 150 years |

## Model Fidelity, σ(Ts) in DJF  

- <date/time>

- Model Fidelity, **σ(Ts)** **in DJF**

**Observation, CAMS**

**Simulation: SST_SNO**

## Model Fidelity, σ(Z200) in DJF  

**NCEP/DOE R2**

**Simulation: SST_SNO**

## Snow Depth Climatology in DJF

- Both are averages for 1979-1987.   For model, assumed snow density 300 kg m-3

**Obs: SMMR**

**Simulation: SST_SNO**

## Comparative Impact  Snow vs SST  

- Analysis of Standard Deviations in DJF

## Δ { σ(Ts) }  in DJF  

**Impact of **
**Snow **
**Variability**

**Impact of **
**SST **
**Variability**

## Δ { σ(Z200) } in DJF  

**Impact of **
**Snow **
**Variability**

**Impact of **
**SST **
**Variability**

##  Δ {σ(Ts), 30°N-60°N}  in DJF  

**Impact of **
**Snow **
**Variability**

**Impact of **
**SST **
**Variability**

## Rotated EOFs of Z200 in DJF,  Atmospheric Modes 

**Rotated EOFs of Z200 in DJF,  Atmospheric Modes**** **

**SST_SNO**

**SST_CSNO**

**EOF 1,   11.6%**

**EOF 2,   11.2%**

**EOF 3,   9.6%**

**EOF 4,   7.3%**

**EOF 1,   13.7%**

**EOF 4,   8.1%**

**EOF 2,    10.7%**

**EOF 5,    7.5%**

## Composite Analysis for Extreme Cases

Impact of Snow Anomaly on the response of Mid-Latitude Climate to Tropical SST Forcing in ENSO Years 

**Impact of Snow Anomaly on the response of Mid-Latitude Climate to Tropical SST Forcing in ENSO Years**** **

## Composite Sfc Temp Anomalies in ENSO Years

**CAMS**

**SST_SNO**

**SST_CSNO**

**SST_SNO - SST_CSNO**

- Yang et al., J Climate, 2001

## Composite Z500 Anomaly in ENSO Years

**SST_SNO**

**SST_CSNO**

## Regression of Z200 and Ts with Nino 3.4 Index  

**SST_CSNO**
**Z200**

**SST_SNO**
**Z200**

**SST_CSNO**
**Ts**

**SST_SNO**
**Ts**

## Why the the variability (Anomalies) of surface air temperature is larger in the runs with interactive snow?

Snow variation can lead to many land surface and atmospheric quantities to change, such as surface temperature, latent and sensible heat fluxes, surface albedo, cloud cover and so on.  These changes also feed back to snow variation (Grossman et al. 1994).  Among all these feedbacks, we found snow-albedo feedback is the most effective one in explaining our GCM results.

- Snow variation can lead to many land surface and atmospheric quantities to change, such as surface temperature, latent and sensible heat fluxes, surface albedo, cloud cover and so on.  These changes also feed back to snow variation (Grossman et al. 1994).  Among all these feedbacks, we found snow-albedo feedback is the most effective one in explaining our GCM results.

## 

**Surface**
**Albedo**

**Surface Downward**
**Solar**

****

**σ  in DJF from SST_SNO,  ****Snow-Albedo Feedback**

**Snow **
**Depth**

**Surface **
**Upward **
**Solar**

## Zonal Mean σ  in DJF from SST_SNO

**Why the greatest impact of snow on sfc temperature **
**variability is found in the mid-latitudes?**

## Amplification by Snow-Albedo Feedback

** ****warmer SST**** **

**warm phase PNA pattern**

**higher surface air temperature**
** **

**less snow**

**smaller  surface albedo**

**more downward solar radiation**

**Amplification by Snow-Albedo Feedback**

## Conclusion: Comparative Impact of Snow and SST, DJF,  Mid-Latitide

|  | Sfc & Lower Tropospheric Temperature | Upper Tropospheric Temperature | Large-scale Circulation | Characteristics |
| --- | --- | --- | --- | --- |
| 
Snow
 | 
larger | 
smaller | Smaller 
(re-order internal modes) | Local;
Snow-albedo feedback etc |
| 
TropicalSST | 
smaller | 
Larger | 
larger | 
Remote;
teleconnection |

## Conclusion:  Mid-Latitude Air-Sea and Air-Snow Interactions at Seasonal time scales

|  | Near Surface Temperature | Upper Tropospheric Temperature | Large-scale Circulation | Mechanism |
| --- | --- | --- | --- | --- |
| 
Air-Snow
 | 
Large | 
small | 
Small
(re-order internal modes) | Snow-albedo feedback amplifies near surface temperature variability |
| 
Air-Sea | 
Large
 | 
Small | 
Small
(re-order internal modes) | Reduction in Thermal damping of near surface temperature Variability by surface energy fluxes  |