# Presentation: 541360

## Influences of the Madden Julian Oscillation on Temperature and Precipitation in North AmericaDuring Weak/Neutral ENSO NH Winters

**Yan Xue, Wayne Higgins and Vernon Kousky**
- Climate Prediction Center, NCEP/NWS
- for the 27th Annual Climate Diagnostics and Prediction Workshop held in Fairfax, Virginia on October 21-25, 2002

## Review

**The MJO has a strong influence on the atmospheric circulation in the tropics and subtropics **
*	**	**Madden and Julian 1971; Weichmann et al. 1985; Lau and Chan 1985; Knutson and Weickmann 1987; Kiladis and Weickmann 1992; Kayano and Kousky 1999*
**The MJO has some influence on the midlatitudes **
**	****( e.g. precipitation events along the west coast of U.S.) **
*	**	**Mo and Higgins 1998; Higgins et al. 2000*

## Approach

**Ten MJO indices are used to describe the eastward propagation of the MJO**
- Real time monitoring
- Composite
- Extreme event frequency anomaly
**Composites are keyed to the convectively active phase of each MJO index**
- Atmospheric circulation
- Temperature
- Precipitation
**Extreme heavy precipitation (>75th percentile), extreme warm (>90th percentile) and cold (<10th percentile) surface air temperature**

## Data

**Pentad data from NCEP/NCAR reanalysis**
- 200-hPa CHI, PSI, u, v.
- 500-hPa Z
- 2.5o latitude/longitude, 1958 – present
**Pentad Outgoing Longwave Radiation**
- 2.5o latitude/longitude, 1979 – present
**Pentad global surface air temperature**
- 	(personal communication with Ping-Ping Xie)
- 2.5o latitude/longitude, 1978 – present
**GPCP global pentad precipitation analysis**
- 2.5o latitude/longitude, 1979 – present

## MJO Indices

**Band-passed (25-87 day) pentad 200-hPa velocity potential (CHI)**
**Extended empirical orthogonal function (EEOF) analysis of the filtered CHI**
- Extended winter (November – April)
- ENSO-neutral and weak ENSO winters (1979-2000)
- 30oS – 30oN, Ten time-lagged patterns
**Projection of the filtered CHI onto the ten patterns of the first EEOF**

## INDEX 1 (80OE)

**INDEX 1 (80****O****E)**

**INDEX 2 (100****O****E)**

**INDEX 3 (120****O****E)**

**INDEX 4 (140****O****E)**

**INDEX 5 (160****O****E)**

**INDEX 6 (120****O****W)**

**INDEX 7 (40****O****W)**

**INDEX 8 (10****O****W)**

**INDEX 9 (20****O****E)**

**INDEX 10 (70****O****E)**

**Notes:**
The first EEOF of the band-passed CHI accounts for 29% of the variance, well separated
from the second EEOF, representing 9% of variance. The blue shade represents the convectively active phases of the MJOs, and red shade the convectively depressed phases. So the period of MJO is about 45 days. 

## Slide 7

| INDEX | 9 | 10 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| LON | 20OE | 70OE | 80OE | 100OE | 120OE | 140OE | 160OE | 120OW | 40OW | 10OW |

## December 2001

- June 2001

**Depth 20****O****C Anom**

## Composite Methodology

**MJO Index > 0.8 sigma (standard deviation)**
- Using multiple pentads around the peaks
-      (3-4 pentads for strong MJOs / 1-2 pentads for weak MJOs)
**Composite is done with unfiltered data but the climatological mean for 1979-1995 was first removed and then the winter season (Dec-Apr) mean are removed.**
**Two-tailed student’s t test (95% significance)**

**Notes:**
The MJO pentads are selected using the MJO indices that are derived with the band-passed CHI. For composites, the data is the unfiltered pentad data with the winter season mean removed. The results are not sensitive to whether the winter season means are removed or not. T test is done by comparing the MJO pentads with the non-MJO pentads during Dec-Apr season in ENSO-neutral and weak ENSO winters in 1979-2000. 

## Slide 10

**Notes:**
Ten MJO indices are obtained by projecting the band-passed CHI onto the ten time-lagged patterns of the first EEOF. Index 1 is the projection onto the first pattern, Index 2 onto the second pattern, .... Here is the ten Indices during 1979-80 winter season from Nov to Apr. The red shade represents the convectively active phases of MJOs. The progression of the red shade from index 1 to 10 represents the eastward propagation of MJOs. Blue dots are the pentads that are used in our composites.

## Composite Members

**Index 1: ****	****80 pentads (29 MJO cases)**
**Index 2: ****	****72 pentads (27 MJO cases) **
**Index 3: ****	****71 pentads (25 MJO cases)**
**Index 4: ****	****70 pentads (26 MJO cases)**
**Index 5:****	****75 pentads (26 MJO cases)**
**Index 6: ****	****78 pentads (28 MJO cases)**
**Index 7: ****	****79 pentads (27 MJO cases)**
**Index 8: ****	****75 pentads (27 MJO cases)**
**Index 9: ****	****67 pentads (25 MJO cases)**
**Index 10: 83 pentads (29 MJO cases)**

**Notes:**
We used 1-4 pentads for each MJO case to maximize sample size. There are 25-29 MJO cases for each MJO index. 

## Seasonality of  MJO

|  | Dec | Jan | Feb | Mar | Apr | Dec-Apr |
| --- | --- | --- | --- | --- | --- | --- |
| Index 1 | 4 | 5 | 6 | 8 | 6 | 29 |
| Index 2 | 3 | 5 | 5 | 7 | 7 | 27 |
| Index 3 | 3 | 4 | 5 | 5 | 8 | 25 |
| Index 4 | 3 | 3 | 6 | 7 | 7 | 26 |
| Index 5 | 4 | 4 | 4 | 6 | 8 | 26 |
| Index 6 | 2 | 6 | 5 | 8 | 7 | 28 |
| Index 7 | 2 | 4 | 4 | 9 | 8 | 27 |
| Index 8 | 3 | 4 | 3 | 9 | 8 | 27 |
| Index 9 | 3 | 4 | 4 | 10 | 4 | 25 |
| Index 10 | 4 | 6 | 5 | 8 | 6 | 29 |
| All Indices | 31 | 45 | 47 | 77 | 69 | 269 |

**Notes:**
MJOs tend to develop more frequently in Mar-Apr than in Dec-Jan. There are only two MJO cases developing in Nov while the teleconnection between the tropics and extratropics is still weak. Due to the limited MJO cases, we used all MJO cases during Dec-Apr for our composites.

## OLR

**OLR**
**cint = 4 w/m****2**

- 20 W/m**2**

**Notes:**
The shaded areas pass the student’s t-test at 95% significance. The blue shade represents enhanced convections, and yellow shade suppressed convections. The OLR composite shows that the initial phase of the MJO cycle is characterized by enhanced convection in far eastern Africa and the Indian Ocean, and suppressed convection in the western Pacific.  As the enhanced convection moves to the maritime continents, the southern Brazil, northern Africa and middle east becomes drier than normal. As the enhanced convection moves to the western pacific, it shifts to the south of the equator. At the same time, a strong suppressed convection develops in the Indian ocean, and an enhanced convection develops in the northern Africa. In the next three pentads, the suppressed convection moves steadily eastward while the enhanced convection in the central Pacific moves little. By the index 8, enhanced convections develop in the southern Brazil and central Africa. By the index 10, a complete cycle is finished in about 45 days.

## 200-hPa Zonal Wind

**200-hPa Zonal Wind**
**cint = 2 m/s**

**Notes:**
The blue shade represents easterly anomalies, and the yellow shade represents westerly anomalies. As the enhanced convection is in the Indian ocean, there are twin anticyclones located to the west and twin cyclones to the east of the tropical forcing, which in turn retracts the East Asian Jet. When the enhanced convection shifts eastward towards the maritime continents (index 3), westerly anomalies near the gulf of Alaska steer moisture air into the Pacific North West, causing wetter-than-normal conditions there and dryer-than-normal conditions in California. As the enhanced convection moves to the western Pacific (index 5), the East Asia Jet extends eastward. As the enhanced convection moves near dateline (index 7 and 8),  westerly anomalies bring moisture air into California, causing wetter-than-normal conditions there and dryer-than-normal conditions in PNW.

## Precipitation

**Precipitation**
**cint = 0.2 mm/day**
- Shading is percentage departure relative to the climatology

**Notes:**
Due to the non-normal distribution of precipitation, the mean of precipitation anomalies is usually non-zero. So we display the difference between the means of MJO and NON-MJO pentads. The shading denotes the percentage departure relative to the climatological pentad precipitation based on the Dec-Apr period (blue for wet and red for dry conditions). When the percentage departure is more than 20%, the field is regarded as significant.

## 500-hPa Height

**500-hPa Height**
**cint = 10 m**

**60 m**

**Notes:**
Strong blocking develops in the north-western Pacific as the enhanced convection is in the Indian ocean. As the enhanced convection moves to the maritime continents, a negative PNA pattern develops, producing warmer-than-normal conditions in the eastern U.S. and colder-than-normal in the western Canada. The negative PNA phase lasts about 2-3 pentads. Around the index 8, a positive PNA pattern is evident, but is much weaker than its counterpart, corresponding to a warm-than-normal condition in the western Canada, but little signal in U.S.. Around the index 9, a ridge develops in the north-western Pacific and a low in the western U.S., corresponding to a colder-than-normal condition in the western U.S.. 

## -1OC

**Surface Air Temperature**
**cint = 0.5****O****C**

**-1****O****C**

- +1**O****C**

## Extreme Frequency Anomaly

**Base pentads**** are composed of all the pentads in the neutral/weak ENSO winters (Dec-Apr) with the ****MJO pentads excluded****.**
**For each MJO index, compute the percentage of the ****MJO pentads**** with pentad amounts ****greater**** than the ****base pentads’ ******** percentile**** (P****mjo****).**
**For each MJO index, compute the ****frequency anomaly**** in percent of expected number of extreme events:**
**	****	****	****P****anom**** = (P****min****/****(**_**1- **__****_******–******

**percent for base pentads**

**Percent for mjo pentads**

**Gershunov and Barnett 1998, J. Climate**

## Extreme Warm (> base 90th percentile) Surface Air Temperature Frequency Anomaly (cint=20%)

**Extreme Warm (> base 90th percentile) Surface Air Temperature Frequency Anomaly (cint=20%)**

**Base 90th percentile distribution**

- -**80%**

- +**80%**

## Extreme Cold (< base 10th percentile) Surface Air Temperature Frequency Anomaly (cint=20%)

**Extreme Cold (< base 10th percentile) Surface Air Temperature Frequency Anomaly (cint=20%)**

**Base 10th percentile distribution**

## Extreme Heavy (> base 75th percentile) Precipitation Frequency Anomaly (cint=20%)

**Extreme Heavy (> base 75th percentile) Precipitation Frequency Anomaly (cint=20%)**

**Base 75th percentile distribution**

## Summary

**Ten MJO indices were calculated as projections of pentad 200-hPa velocity potential onto ten time-lagged patterns of the first EEOF.**
**Keying on the convectively active phases of the ten MJO indices, ten composites of the MJO events during ENSO-neutral and weak ENSO winters were constructed for various fields.**
**Significant MJO-related influences on both means and extreme events of surface air temperature and precipitation in the North America are found.**

**Notes:**
Show the schematic plot instead of the long sentences when Mike Halpert finishes it.