Interferential Impact of ENSO and PDO
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Interferential Impact of ENSO and PDO on Dry and Wet Conditions in the U. S. Great Plains Zeng-Zhen Hu 1 Bohua Huang 1,2 1 Center for Ocean-Land-Atmosphere Studies Calverton, Maryland, USA 2 Department of Atmospheric, Oceanic, and Earth Sciences College of Science, George Mason University

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Interferential Impact of ENSO and PDO on Dry and Wet Conditions in the U. S. Great Plains

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Interferential impact of enso and pdo on dry and wet conditions in the u s great plains

Interferential Impact of ENSO and PDO on Dry and Wet Conditions in the U. S. Great Plains

Zeng-Zhen Hu1

Bohua Huang1,2

1Center for Ocean-Land-Atmosphere Studies

Calverton, Maryland, USA

2Department of Atmospheric, Oceanic, and Earth Sciences

College of Science, George Mason University

Fairfax, Virginia, USA

COLA

??


What you can get from this presentation

What you can get from this presentation?!

(1) Impact of ENSO US climate(you already know)

(2) Influence of PDO on US climate(you may be an expert)

(3) Interferential impact of ENSO and PDO on US climate(you may be familiar with it)

(4) Interferential impact of ENSO and PDO on dry/wet conditions over the US Great Plains, particularly the mechanisms, seasonality and its interpretation

You will get nothing new from this presentation, if you already know (4)


Objectives

Objectives:

  • What are the large-scale patterns of anomalies associated with dry/wet conditions in the North America (Great Plains)?

  • What is the interferential impact of ENSO and PDO on the U. S. Great Plains and the seasonality?

  • How to interpret the interferential impact and its seasonality?


Data i

Monthly global analyses of precipitation over land on a 2.5ox2.5o, referred to as precipitation reconstruction (PREC) (Chen et al. 2002)

Monthly soil wetness data (top 1.3m), 0.5ox0.5o (Fan and van den Dool 2004)

NCEP/NCAR reanalysis, 2.5ox2.5o (Kalnay et al. 1996)

SST dataset, the extended reconstruction (ER-v2), 2ox2o (Reynolds et al. 2002)

Nino3.4: SST anomalies in 5oS-5oN, 170o-120oW

Data I


Data ii

The Pacific Decadal Oscillation (PDO) index is defined as the leading principal component (PC) of North Pacific monthly SST variability (poleward of 20oN) (Zhang et al. 1997; Mantua et al. 1997).

The monthly mean global average SST anomalies are removed prior to PC decomposition to separate PDO related variability from any “global warming" signal that may be present in the SST data.

The PDO index represents a long-lived El Niño-like pattern of SST anomalies in the tropics with broader meridional scale, which is linked to a North Pacific SST pattern with opposite SST anomalies between the central Ocean and eastern boundary. The mode oscillates on interannual and interdecadal timescales.

The standardized values for the PDO index are downloaded from http://jisao.washington.edu/pdo/PDO.latest.

Data II

Warm (Positive) Phase

Cold (Negative) Phase


Data iii

All the data span Jan. 1950-Dec. 2005

Using monthly data to do all the analyses, different from those works basing on the episodes/phases of PDO (such as, Gershunov and Barnett 1998, so on)

PDO phases: Index >0.5(warm); < -0.5 (cold); others (neutral)

ENSO phases: Index >0.5(El Niño ); < -0.5 (La Niña); others (neutral)

The Great Plains: SW >0.5 (wet); <-0.5 (dry); others (neutral)

Data III


Define dry and wet conditions in the u s great plains i

Define dry and wet conditions in the U. S. Great Plains (I)

SW onto SW

PREC onto PREC


Lag lead and cross correlations of soil wetness and precipitation in the great plains

Lag/Lead and Cross Correlations of Soil Wetness and Precipitation in the Great Plains

Soil Wetness

Precipitation

P leading SW

P lagging SW

1 month


Interferential impact of enso and pdo on dry and wet conditions in the u s great plains

Dry&Wet in the Great Plains associated with LARGE scale anomaly patterns of SST and SLP (ENSO, PDO, AO/NAO)

SST

SLP

Wet

Dry

Wet-Dry


Similarity and difference between pdo and enso dominant time scales

Similarity and difference between PDO and ENSO (dominant time scales)

CC=0.58

Interdacadal

About 1year


Lag lead and cross correlation of the pdo and nino3 4 indices

Lag/Lead and Cross Correlation of the PDO and Nino3.4 Indices

Nino3.4 Index

PDO Index

Nino3.4 leading PDO

Nino3.4 lagging PDO

2-5months


Cross correlation of the pdo and nino3 4 indices with soil wetness in the great plains

Cross Correlation of the PDO and Nino3.4 Indices with Soil Wetness in the Great Plains

Nino3.4 leading SW

Nino3.4 lagging SW

1-2 Months

PDO lagging SW

PDO leading SW

1 Month


Enso and pdo show a similar impact pattern

ENSO and PDO show a similar impact pattern

ENSO

PDO

ENSO

-PDO

SLP/U&V

SST

SW


Composite for warm pdo 0 5

Composite for Warm PDO (≥0.5)

El Niño

La Niña

Neutral

SLP/U&V

SST

SW


Composite for cold pdo 0 5

Composite for Cold PDO (≤-0.5)

La Niña

El Niño

Neutral

SLP/U&V

SST

SW


Composite for neutral pdo 0 5 pdo 0 5

Composite for Neutral PDO (-0.5<PDO<0.5)

El Niño

La Niña

Neutral

SLP/U&V

SST

SW


Different impact of in phase and out of phase of enso and pdo

Different impact of in-phase and out-of-phase of ENSO and PDO

++

In Phase

±

Out of Phase

In-Phase-

Out-of-Phase

SLP/U&V

SST

SW


Interferential impact of enso and pdo on dry and wet conditions in the u s great plains

In-phase of ENSO and PDO favors Great Plains drought/floodOut-of-phase of ENSO and PDO favors Great Plains neutral

PDO

NINO3.4


Relative frequency of dry neutral and wet conditions in gp for different enso and pdo combinations

Relative frequency of dry, neutral, and wet conditions in GP for different ENSO and PDO combinations

Absolute Fr

Relative Fr.

Warm PDO

Cold PDO

Neutral PDO


Wave activity v at 200 hpa

Wave Activity (v*) at 200 hPa

ENSO+PDO

ENSO

ENSO-PDO

PDO


Seasonality robust but mam strongest son weakest

Seasonality: Robust; but(MAM=Strongest; SON=Weakest)

MAM:

Strongest

PDO

SON: Weakest

Nino3.4


Explaining the seasonality of the impact

Explaining the Seasonality of the Impact

Strong

In

Between

Positive


Interferential impact of enso and pdo on dry and wet conditions in the u s great plains

Summary I:The relationship between ENSO or PDO and climate anomalies in the Great Plains is intensified when ENSO and PDO are in phase (El Niño&warm PDO, or La Niña&cold PDO).On average, the Great Plains favors anomalous wet (dry) conditions when both ENSO and PDO are in the positive (negative) phase. However, the relationship is weakened when ENSO and PDO are out of phase (El Niño&cold PDO, or La Niña&warmPDO). Without ENSO, PDO alone does not affect the North American climate significantly.Seasonality: robust, but, spring is the strongest; autumn is the weakest; summer and winter fall in-between. That is associated with the mean seasonal cycle in the North Pacific.


Interferential impact of enso and pdo on dry and wet conditions in the u s great plains

Summary II(in-phase up/low level circulation)The contrasting impact of the interference of ENSO and PDO on the North American climate anomalies is associated with the differences in the ocean-atmosphere anomalies. When ENSO and PDO are in phase, the SST anomalies extend from the equatorial Pacific to the high latitude part of the North Pacific via the eastern ocean. The distribution of the corresponding anomalies of SLP and the wind at 1000 hPa forms an ellipse with a southeast-northwest orientation of the long axis.At upper troposphere, two similar wave trains with the same sign associated with PDO and ENSO are overlapped and intensified.


Interferential impact of enso and pdo on dry and wet conditions in the u s great plains

Summary III (out-of-phase up/low level circulation)However, when ENSO and PDO are out of phase, the SST anomalies have the same sign in the tropical and North Pacific, which are opposite to the anomalies in the regions near the west coast. The anomalously cyclonic circulation over the North Pacific is weaker in the out-of-phase situation than in the in-phase situation. The distribution of the anomalies of SLP and the wind at 1000 hPa resembles a circle.At upper troposphere, two similar wave trains with opposite sign associated with PDO and ENSO are canceled and weakenedThe differences in the eastern part of the North Pacific between in-phase and out-of-phase based on ENSO and PDO may suggest an overlap of the signals associated with PDO and ENSO-induced coastal Kelvin waves.


In phase enhancement

PDO and ENSO

In-Phase Enhancement

Out-of-Phase Cancellation

PDO

PDO

-

+

ENSO

ENSO

Costal Kelvin Waves


Interferential impact of enso and pdo on dry and wet conditions in the u s great plains

Hu, Z.-Z. and B. Huang, 2009: Interferential impact of ENSO and PDO on dry and wet conditions in the U. S. Great Plains, J. Climate (revised). (Email: [email protected])


Interferential impact of enso and pdo on dry and wet conditions in the u s great plains

Hu, Z.-Z. and B. Huang, 2009: Interferential impact of ENSO and PDO on dry and wet conditions in the U. S. Great Plains, J. Climate (revised). (Email: [email protected])


Explaining the seasonality of the impact i

Explaining the Seasonality of the Impact (I)


Explaining the seasonality of the impact iii

Explaining the Seasonality of the Impact (III)


Define dry and wet conditions in the u s great plains ii

Define dry and wet conditions in the U. S. Great Plains (II)

SW onto PREC

PREC onto SW


Enso and pdo show a similar impact pattern on us drought floods monthly data 1950 2005

ENSO and PDO show a similar impact pattern on US drought/floods (monthly data: 1950-2005)


Interferential impact of enso and pdo on us drought floods

Interferential Impact of ENSO and PDO on US drought/floods


Wave activity flux

Wave Activity Flux


Wave activity flux1

Wave Activity Flux


Relative frequency of dry neutral and wet conditions in gp in different enso and pdo combinations

Relative frequency of dry, neutral, and wet conditions in GP in different ENSO and PDO combinations

PDO≥0.5

PDO≤-0.5

0.5>PDO>-0.5

ENSO≥0.5

ENSO≤-0.5

0.5>ENSO<-0.5


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