# Presentation: 747272

## RADAR-OBSERVED CHARACTERISTICS OF PRECIPITATING SYSTEMS  Tim Lang, Dave Ahijevych, Steve Nesbitt, Rit Carbone Steve Rutledge, Rob Cifelli

**RADAR-OBSERVED CHARACTERISTICS OF PRECIPITATING SYSTEMS  **Tim Lang, Dave Ahijevych, Steve Nesbitt, **Rit Carbone** Steve Rutledge, Rob Cifelli

**CSU****      ****NCAR**

## GUASAVE

- CABO
- SAN LUCAS

- S-Pol

## Slide 3

## The Rainfall Timeseries

## 31 Jul

**31 Jul**

**1 Aug**

**2 Aug**

**3 Aug**

**4 Aug**

**5 Aug**

**6 Aug**

## Composite Reflectivity from 00 Z 5 Aug - 00 Z 7 Aug

**Composite Reflectivity from 00 Z 5 Aug - 00 Z 7 Aug**

- Diurnal Cycle**                ****43 day period of record**

- Diurnal Cycle
**Regime A (14) vs Other Days (29)**

## Diurnal CycleRegime B (14) vs Other Days (29)

- Diurnal Cycle**Regime B (14) vs Other Days (29)**

## Period of Record StatisticsIt rains more on regime days and the rain is mainly from organized convection.

## Diurnal StatisticsIt rains more on regime days, most of the rain is from organized convection.

## Diurnal StatisticsStratified by locationOpposing phases of organized convection over land and sea  

## More Shear, Stronger SE Wind

## Easterly Waves and Humidity

## Preliminary Conclusions

-    Most rainfall is triggered by the SMO heat source and sea breeze.
-    Intraseasonal variability appears to be systematic.
-    Surges were associated with a small fraction of this variability and may not 	be as important to the big picture as originally hypothesized.
-    The A, B, and AB Regimes are associated with the capacity for 	convection to organize, scale upwards and propagate.
-    Regime days have enhanced shear, enhanced CIN, and *ordinary* CAPE.
-    The organized convection produces more rainfall, and propagates with 	respect 	to the local forcings and the steering winds (~6m/s).
-    Propagation, combined with triggering by the elevated heat source, leads to 	a well defined pattern of the diurnal cycle (“globally phase locked”).
-    Rainfall patterns are also consistent with the GoC acting as a nocturnal 	heat source and the land breeze front as “triggering topography”.

***New convective parameterizations are needed to get this stuff right.***

## These findings are part of a larger picture...

##  RESULTS published, emerging, analysis in progress, new study

**Continental Warm Season Rainfall Studies**

- Background after Laing and Fritsch 1997

## “EPISODES”Sequences of convective systems often result from a coherent  regeneration of organized convection.  “Episodes” span substantial distances over North America on a daily basis in summer.(~1000 km, 20 h)

**“****EPISODES”****Sequences of convective systems often result from a coherent  regeneration of organized convection.  ****“Episodes” span substantial distances over North America on a *****daily***** basis in summer.****(~1000 km, 20 h)**

**Radar **<**Rainrate**>

**Original US Findings, JAS 2002**

## Diurnal Cycle     July 1997

**Longitude**

**Diurnal Cycle     ****July 1997**

**% Time Radar Precipitation Echo**

**We refer to this      pattern as            “globally phase-locked”**

- Essentially all forcing is diurnal.
- Effects are both local and remote.
-  Remote effects result from coherent regeneration of convection and propagation

**Original US Findings, JAS 2002**

**Notes:**
Clear 2nd day signal

## AFRICA: NH Summer (5S – 20N)

**AFRICA****: NH Summer (5S – 20N)**

- Diurnal Cycle: July 1999

**UTC**

- 1 – 7 July 1999

**Arlene Laing **

**UTC**

## RADAR-OBSERVED CHARACTERISTICS OF PRECIPITATING SYSTEMS  Tim Lang, Dave Ahijevych, Steve Nesbitt, Rit Carbone Steve Rutledge, Rob Cifelli

**RADAR-OBSERVED CHARACTERISTICS OF PRECIPITATING SYSTEMS  **Tim Lang, Dave Ahijevych, Steve Nesbitt, **Rit Carbone** Steve Rutledge, Rob Cifelli

**CSU****      ****NCAR**

- THANKS!