# Presentation: 195815

## NO2 results from the  DANDELIONS-Field Campaign                   Ellen Brinksma                             & the Dandelions team

**NO****2**** results from the  DANDELIONS-Field Campaign****                   ****Ellen Brinksma ****                            & the Dandelions team**

_**D**_**utch **_**A**_**erosol and **_**N**_**itrogen **_**D**_**ioxide **_**E**_**xperiments ****for Va**_**li**_**dation of **_**O**_**MI a**_**n**_**d **_**S**_**CIAMACHY**

## DANDELIONS Project

- OMI tropospheric NO2
- October 2004
- (F. Boersma, KNMI)

- Aerosol Optical Depth (555 nm)
- August 2000 (TNO)

** ****Satellite validation under **
**polluted conditions (Netherlands)**

## Validation over the Netherlands
OMI aerosol OD & ssa  (AATSR)
OMI and SCIAMACHY NO2 

Additional groundbased measurements performed to 
Check altitude info used in algorithms
Check aerosol characteristics

Two-year (2004-2006) project funding by (Dutch) USP2 for 1 postdoc  & 1 PhD student
Campaign planned as part of this project	

OMI Science Question: 
What are sources & transport of tropospheric constituents?		

- OMI aerosol OD & ssa  (AATSR)
- OMI and SCIAMACHY NO2
- Additional groundbased measurements performed to
- Check altitude info used in algorithms
- Check aerosol characteristics
- Two-year (2004-2006) project funding by (Dutch) USP2 for 1 postdoc  & 1 PhD student
- Campaign planned as part of this project
- OMI Science Question:
- What are sources & transport of tropospheric constituents?

**DANDELIONS Project**

## DANDELIONS Campaign May-July 05

**DANDELIONS Campaign May-July 05**

- Cabauw (51 N, 5 E)
- 5 “golden days” (extensive analysis) – cloud fraction < 0.2
- Many continuous measurements
- Suite of aerosol instruments (next)
- Suite of NO2 instruments (next)
- Additional ozone sondes (De Bilt)
- Brewer De Bilt (O3, NO2)
- Radiometers focused at radiation and cloud studies
- Full meteorological info at location

**OMI (and SCIA) validation of aerosols, NO****2**** (total & trop), + ozone**
**Intercomparison of groundbased NO****2**** measurements**

## NO2  Instrumentation

- OMI, SCIAMACHY
- RIVM lidar (DIAL) system – profile 2.5 km
- NL ground sampler network, includes Cabauw
- MAX-DOAS instruments yield tropospheric NO2 columns, twilight total columns, limited altitude info
- Chimere, Aurora regional models
- UHeidelberg: Three telescopes, so three viewing  directions
- Five MAXDOAS systems (3 + 2 mini)
- BIRA systems 300 m from UBremen & UHeidelberg systems;
- KNMI miniMAXDOAS beside BIRA & (few days) beside UBremen
- BIRA mini system beside BIRA, later in tower (220 m)

## Measure solar spectra at different telescope elevations, light path length in the troposphere differs for different elevations 
DOAS method to retrieve daytime slant columns

Relate to midday zenith spectrum & use airmass factors:  tropospheric vertical columns 

Optimal estimation: daytime        0-2.5 km vertical profiles can be derived 

Twilight measurements used for stratospheric columns (conventional DOAS method)

- DOAS method to retrieve daytime slant columns
- Relate to midday zenith spectrum & use airmass factors:  tropospheric vertical columns
**Optimal estimation: daytime        0-2.5 km vertical profiles can be derived **
- Twilight measurements used for stratospheric columns (conventional DOAS method)

- MAX – DOAS = _M_ulti – _AX_is – DOAS

**MaxDOAS**

## Lidar technique 

**Lidar technique**** **

- Lidar, but multi-angle observations to
-  increase sensitivity for lower altitudes
-  measure below “overlap altitude” (700 m)

## 

May 27, 28:   cloudless, high aerosol and NO2 load (continental). See interesting change in lidar NO2 profiles during May 28. 
June 19: cloudless, very clear –  virtually no aerosols (BL lidar, Aeronet) or NO2 (lidar). No ozone sonde from De Bilt.
June 23: almost cloudless (little haze)
June 24: milky blue sky and some cirrus. Very high aerosol loading (CIMEL)

Two other candidate days had cloud fractions 0.3 and 0.5
Two days with excellent weather were missed for logistic reasons

- May 27, 28:   cloudless, high aerosol and NO2 load (continental). See interesting change in lidar NO2 profiles during May 28.
- June 19: cloudless, very clear –  virtually no aerosols (BL lidar, Aeronet) or NO2 (lidar). No ozone sonde from De Bilt.
- June 23: almost cloudless (little haze)
- June 24: milky blue sky and some cirrus. Very high aerosol loading (CIMEL)
- Two other candidate days had cloud fractions 0.3 and 0.5
- Two days with excellent weather were missed for logistic reasons

**Golden Days**

## Nitrogen Dioxide Results

**Nitrogen Dioxide ****Results**

## IUP Bremen: Tropospheric NO2 vs. in-situ

- Columns derived from simple approximations
- measurements for all days, not only for clear sky
- high values 0.5 - 4  1016 cm-2
- large variability but no random fluctuations

**N****eed for comparison with profile retrieval and correlative measurements**

## BIRA MAXDOAS tropospheric NO2 vs. SCIAMACHY

- BIRA MAX-DOAS tropospheric NO2 retrieved with geometrical AMFs
- SCIAMACHY tropospheric NO2 from KNMI/BIRA   ( www.temis.nl )

## Mini MAX-DOAS

- Comparison between two mini-DOASes and the BIRA MAX-DOAS, measuring side-by-side

## MAX-DOAS 0 & 220 m

**MAX-DOAS 0 & 220 m**

- 5 July 2005: installation on top of the Cabauw mast

- Comparison of one full elevation scan, as measured from the ground and from 220 m altitude. From the combination of both instruments, one expects increased information content for profile retrieval.

## Heidelberg telescopes

- Directions of the Heidelberg telescopes

**Telescopes at different azimuth angles allow to detect horizontal gradients**

- 1° elevation

- Thomas Wagner, Ossama Ibrahim

- Most days, more pollution towards S
- Some days, no horizontal gradients

## Comparison Bremen & BIRA

- different viewing directions, different time of measurement
- => very good consistency!

## May 28 (polluted “golden day”)

- Consecutive NO2 profiles (lidar)
- In situ sampler

- I: 10.15 UT

- III: 13.25 UT

- II: 12.00 UT

- Note large variation in profile shape, and
- rapid decrease of ground concentrations

## MAXDOAS NO2 profiles: kernels

**Optimal estimation **
**1 hour average**
**Cloud-free only**
**All viewing angles**
**Trace = 4.8 measure for in number of independent layers**
**Forward calc. with SCIATRAN**
**Aerosol corrections from O4 retrieval**

**Averaging Kernels for 13 May 2005**
**IUP Bremen, A. Richter et al.**

- Height [km]

## Profile retrieval from MAXDOAS

## Comparison in-situ IUP Bremen MAXDOAS

- BREAM profile retrieval
- value for lowest 50 m
- aerosol OD from O4 signal
- data selection based on NO2 and O4 consistency with RTM simulation for all viewing directions

**excellent agreement both in relative and absolute terms**
**no scaling or free parameters**
**MAXDOAS can link in-situ and satellite measurements**
**(F.Wittrock / A. Richter)**

## Conclusions & Outlook

**Conclusions ****& ****Outlook**

## Measurement statistics

- Operator-assisted:
- NO2 lidar 14 days
- ozone sondes 14
- radio sondes 8.
- Continuous records:
- MaxDOAS (3 instruments)
- CIMEL (2 instruments)
- miniDOAS (2 instruments), for part of campaign
- permanent instruments at Cabauw.
- Satellite overpasses (within 51 days, May 12–Jun 30):
- OMI 79
- SCIAMACHY 24
- AATSR 16.

## Conclusions

- Campaign was very successful
- SCIAMACHY & MaxDOAS trop NO2 agree well
- Preliminary OMI AOD were not good enough to base conclusions on – provisional release will be better (calibration, ground albedo)!
- MaxDOAS instruments compare well when side-by-side, reasonable if 300 m apart
- NO2 field often higher towards South, many short-time fluctuations seen
- Unique NO2 profiles 0-2.5 km (lidar, MAXDOAS)

## Outlook

- NO2 profile comparisons: MAXDOAS, lidar, OMI, SCIAMACHY, Chimere regional model, Aurore hi-res model
- Closure-type studies for five golden days
- Validation of OMI and SCIAMACHY total & tropospheric columns
- Campaign report on MaxDOAS results available soon on Accent-Troposat 2 website

## The Dandelions team:

**The Dandelions team:**

**KNMI: ****	****	****E. Brinksma, P. Levelt, R. Rothe, E. Worrell, ****	****	****A. Swinkels, S. Warmer, A. Piters, R. Agterberg, ****	****	****M. Allaart,  M. Kroon, J. de Vroom, H. Eskes, ****	****	****F. Boersma, P. Veefkind, N. Léonard-Blond, ****	****	****C. van Oort, H. Welberge, and many others ... ****TNO The Hague:**** ****	****G. de Leeuw, L. Curier, M. Moerman****RIVM:**** ****	****	****D. Swart, S. Berkhout, R. van der Hoff, H. Bergwerff, ****	****	****A. Apituley and others****BIRA-IASB:**** ****	****M. van Roozendael, C. Fayt, C. Hermans, G. Pinardi****IUP Heidelberg:**** ****	****T. Wagner, O. Ibrahim****IUP Bremen:**** ****	****A. Richter, H. Oetjen, F. Wittrock****	****	****Acknowledgments:**** **** ****    AT-2 for providing travel grants ****    ****    Dutch User Support (GO) programme for project funding** **    ****Guidance meteorologists & computer technicians at KNMI**

## Backup Material

**Backup Material**

##          May 27, 2005                               June 19, 2005 

**May 28, 2005**

- 4-day backtrajectories @ 200,500,_**700,800,900**_ hPa
- Continental pollution May 27, 28                 Very clean air June 19
- 					             Very polluted June 24
- 			 	Courtesy of Rinus Scheele, KNMI

**June 23, 2005**

## DANDELIONS Aerosols

- _Aerosol instrumentation_

- Validation of OMI, AATSR
- Various sun photometers (CIMEL, SPUV, Globe)
- Volatility system, aethalometer, 3-wavelength nephelometer, size distributions 10 nm – 10 μm
- Tropospheric backscatter lidar
- Radio sondes (RH, T, P, for aerosol swelling with height)

## Correlation OMI & in situ NO2

- Boersma et al, KNMI