# Presentation: 870745

## Decadal Forecasting Of UV Dosage Levelsat the Surface: Aura, Airborne, Ground-based, and Modeling

- EOS Aura Science Team Meeting
- Pasadena, CA
- February 28─March 3, 2005
- Jim Anderson
- Rick Stimpfle, Dave Wilmouth, Jasna Pittman,
- Tom Hanisco, Liz Moyer, Frank Keutsch, Ryan Spackman
- Elliot Weinstock, Dave Sayres,
- Harvard University

## NRC Decadal Report Requested by NASA and NOAA

- PHASE I
- _Earth Science and Applications from Space:_
- _Urgent Needs and Opportunities to Serve the Nation_
- Explicitly Identify the Critical Importance of Societal Objectives
- Emphasize the Required Decision Support Structure

## Presidential Initiatives

- US Climate Change Science Program: Strategic Plan
- Reduce uncertainty in projections of how the Earth’s climate and related systems may change in the future;
- Understand the sensitivity and adaptability of different natural and managed ecosystems and human systems to climate and related global changes; and
- Explore the uses and identify the limits of evolving knowledge to manage risks and opportunities related to climate variability and change
- Global Earth Observation Initiative: 2003
- Vision for Space Exploration

## Slide 4

## ADDRESSING THE SOCIETAL OBJECTIVE OF FORECASTING UV DOSAGE REQUIRES:

- Restructuring the connection between forecast modeling, satellite observations and *in situ* and ground based observations: common coordinate system, high accuracy observations, data assimilation, systematic testing of forecast output, workshop structure that joins to an operational plan to deliver required input to the decision process.
- Reassessment of the sophistication and credibility of the observations that are required to develop a picture of this system – to understand the specific mechanisms responsible for S/T exchanges, the coupling of the tropics to the sub-tropics, the role of the middle world in meridional exchange, the dominant rate limiting catalytic cycles, the convective coupling of troposphere to the TTL,etc. – that is tested and trusted leading to a forecast that is credible.

## Slide 6

## Central tenet in the latest WMO report: Scientific Assessment of Ozone Depletion: 2002 In the Scientific Summary for the key Chapter 4, under, “Attribution of Past Changes in Ozone,” on page 4.2, it is stated:“The vertical, latitudinal, and seasonal characteristics of changes in mid-latitude ozone are broadly consistent with the understanding that halogens are the primary cause of these changes, in line with similar conclusions from the 1998 Assessment.”

## Sensitivity of Ozone Trends to Bromine

- Enhanced Bromine:
-        increase in computed ozone depletion
-        better agreement with observation

**Br****y****TROP**** = 8 ppt model**
**accounts for ~94%**
**of observed O****3**** depletion**
**in the N.H.**

**Notes:**
Explain that the tabular numbers are area between the zero line and the model/data, divided by the length of the record (1980 to end 2000)
SH more complicated: results shown in our paper.

## Ozone Photochemistry

- Enhanced Bromine:
-        **** ozone depletion due mainly to BrO+ClO cycle
-        BrO+HO2 cycle becomes significant O3 sink below 16 km
-        (BrO+HO2 does not drive O3 depletion if BryTROP is constant over time)

- BryTROP = 0 ppt

- BryTROP = 8 ppt

** ****AER Model Time Slice: 47****°****N, March 1993**

**Notes:**
BrO+HO2 also is responsible for significant reductions in computed global tropospheric O3 => von Glasow et al., ACP, 2004

## Slide 10

## David Wilmouth’s Poster Images

## Sensitivity of Ozone Trends to Bromine

- Enhanced Bromine:
-        increase in computed ozone depletion
-        better agreement with observation

**Br****y****TROP**** = 8 ppt model**
**accounts for ~94%**
**of observed O****3**** depletion**
**in the N.H.**

**Notes:**
Explain that the tabular numbers are area between the zero line and the model/data, divided by the length of the record (1980 to end 2000)
SH more complicated: results shown in our paper.

## Slide 13

## Slide 14

## Slide 15

## Solomon et al., “Heterogeneous chlorine chemistry in the tropopause region,” J. Geophys. Res. 102, 21,41129, 1997.

- Solomon *et al.,* “Heterogeneous chlorine chemistry in the tropopause region,” *J. Geophys. Res.* 102, 21,41129, 1997.

## Slide 17

## Sensitivity of Ozone Trends to Bromine

- Enhanced Bromine:
-        increase in computed ozone depletion
-        better agreement with observation

**Br****y****TROP**** = 8 ppt model**
**accounts for ~94%**
**of observed O****3**** depletion**
**in the N.H.**

**Notes:**
Explain that the tabular numbers are area between the zero line and the model/data, divided by the length of the record (1980 to end 2000)
SH more complicated: results shown in our paper.

## Slide 19

## Slide 20

## IPCC 4AR dq/dt: Difference Between Model Forecasts

**IPCC 4AR dq/dt: Difference Between Model Forecasts**

## What Characterizes the Eocene?

- Warm deep ocean temperatures: 10 K warmer than at present
- Warm polar sea surface temperatures
- Northern Hemisphere continental interiors were warm enough throughout year to sustain palm trees and tropical flora/fauna to northern Canada
- Continental glaciation absent
- Tropical temperatures similar to present

## Sloan and Pollard [1998] imposed optically thick PSCs in a GCM in combination with increased greenhouse gas concentration.

Wintertime warming of 	4 K at mid latitudes
				20 K at polar latitudes
Origin of PSCs? Methane

PROBLEM: Eocene warmth uninterrupted for 10 million years

Evidence for episodic release from isotopes, but not sustained release

- Sloan and Pollard [1998] imposed optically thick PSCs in a GCM in combination with increased greenhouse gas concentration.
- Wintertime warming of 	4 K at mid latitudes
- 				20 K at polar latitudes
- Origin of PSCs? Methane
- PROBLEM: Eocene warmth uninterrupted for 10 million years
- Evidence for episodic release from isotopes, but not sustained release

## Feedback Between CO2, Stratospheric Overturning, and 				Stratospheric H2O

- When CO2 increases, GCMs predict increasing  surface warming in the polar regions from ice/snow albedo feedback
- This leads to reduced equator-to-pole temperature gradient (*T**eq*  *T**p*), potentially in concert with ocean/atmos heat flux changes
- This leads to reduced excitation of gravity and planetary waves (*A*), Reduced wave breaking in the stratosphere diminishes the delivery of momentum (*M*) to the stratosphere
- This decrease in overturning results in an increase in the temperature of the cold-point tropopause (*T**T*)

## IPCC 4AR dT/dt: Difference Between Model Forecasts

**IPCC 4AR dT/dt: Difference Between Model Forecasts**

## Global Climate Benchmark MeasurementsOccultation methods: How they work

- [Basic figures from D. Feng, Univ. of Arizona, private communications, 2001 (modified)]

**Global Climate Benchmark Measurements****Occultation methods: How they work**

***Occultation methods***
- Exploit extinction and/or refraction of electromagnetic signals along limb paths
- Providing _self-calibrated measurements_ of  transmission and/or Doppler shift profiles
- Leading via opt. thickness or column density, bending angle, and (complex) refractivity
- To key atmospheric and climate parameters such as temperature, humidity, ozone, and geopotential height (among others)

## GPS Occultation: The Time Standard

- GPS occultation is tied to ground-based atomic clock standards by double-differencing technique.
- NIST F1 measures time with fractional error of 1.7•10-15 (as of 1999).

## Radiosondes and GPS Occultation

## COSMIC

- Six satellites in three 72° orbit planes
- > 3000 soundings per day
- Launch in 2005
- Taiwan, NSF (UCAR)

- Five days’ worth of COSMIC occultations with GPS orbits as of June 1, 2004.

## Slide 30

## STRAT/TROP EXCHANGE and TRANSPORT PATHWAYS at this MEETING

- Convection on Clouds and Water Vapor in the TTL – Pfister
- Convection on Summertime Extratropical LS from Aura – Dessler
- Transport Pathways into Subtropical LS – Pittman
- Accuracy of water vapor and total water via laboratory and intercomparison – Weinstock, Spackman
- Isotopic composition of the TTL, lower stratosphere, middleworld – Moyer, Hanisco, Keutsch

## II. ELEMENTS OF THE FORECAST

- Form a Consortium to Develop the Forecast Structure Establishing Priorities for Required Satellite, Airborne, and Modeling Components
- Address, in Terms of the Required Objectives, What Level of Sophistication is Required for the Observations that will Result in a Forecast That is Tested and Trusted
- Establish a Systematic Analysis of the Intrinsic Quality of the Data That Enters the Analysis – just as we have with laboratory kinetics and photochemistry data
- Decide on how the Operational Forecast will be Tested  and How it will be Systematically Improved
- Build Union with Medical Community to link UV Dosage to Human Health
- Assume Responsibility for the Long-Term Forecast