Yesterday, Fr 24-10-2014, was a realy nice measurement day. A lot of mid-level clouds over Cabauw and all instruments where running and measuring smothly. Only the lidar systems where not able to penetrate the clouds, because of the precipitation that was present during the whole day. The overpassing front systems produced the whole day real nice clouds that we measured. To capture the vertical structure of the cloud system and the atmosphere we launched some radiosondes. So all in all we are happy that we could measure this clouds. With those information I wish a nice weekend!
The last days have been quite windy and rainy. That is also the reason why we didn’t spend so much time on the site. We launched some days ago some weather balloon. Such a radiosonde takes about 30 minutes of preparations before it is launched. First the balloon has to be filled with the right amount of Helium. Then the parachute attached and finally the sonde itself has to be tied up to the parachute. One important point to take into account before the launch is the wind speed and the direction. This prevents the sonde from being caught by trees or one cable of the Cabauw tower.
With such a radiosonde it is possible to get vertical information about temperature, pressure, humidity and wind as the balloon is ascending in the atmosphere. This information help us to define thermodynamic conditions under which some of the microphysical processes can take place and some don’t. Several launches after each other also contain information about the variability of the atmospheric state. So all in all this small device is a real useful tool for our campaign.
In July this year ATMOS group attended the 14th Conference on Cloud Physics and 14th Conference on Atmospheric Radiation which were held together in Boston. The conference is organised by the American Meteorological Society every 3 years. It is one of the biggest conferences in Cloud Physics and Radiation field.
We were presenting two posters:
- How Can We Use Lidar And Radar To Monitor Aerosol-Cloud Interaction? presented by Karolina Sarna
- The satellite observation of drizzle in Stratocumulus clouds presented by Igor Stepanov
If you are interested in the recordings from the Conference or Extended Abstracts, have a look here:
On Monday, we had a visit form a photographer (Rob Doolaard) to shoot some pictures from our work there. Because of ‘bad’ weather conditions, we were most of the time inside one of the instrumental cabins to prepare our daily meeting and later on to also do the meeting. Actual plan had been, that we do lidar measurements and launch a weather balloon as well, but the conditions were too bad, so we skipped it. The first two pictures are taken inside the TARA radar cabi. The other two are outside during one of our discussions. They illustrate quite well, that a measurement campaign includes a lot of ‘IDLE state’ as well. And if the weather is not nice you wait inside 🙂
Now the first week is over already. It was an interesting one and we learned a lot from it.
One thing is that hardware for wireless connection is not always waterproof. So we bought new ones and installed them and now everything works again. Network problems also costs us some missing of raw-data with TARA yesterday, but now everything seems to work again. The biggest issue we had so far is that both cloud radars stop working at the same. So right now we try to repair them with the support from METEK. One is already back and measuring. For the second on we hope to get it done soon.
We also performed our first measurements with CAELI on Friday. We took almost 3 hours of measurements with it. At the beginning some low cumulus clouds were present. This made it difficult to align the lidar properly but after a short stop and a short readjustment it worked fine. Also in the afternoon the low cloud disappeared and we could measure the cirrus clouds.
All in all the first week was quite busy and I hope that the next weeks will be busy as well. But it would be nice to have less errors to fix and take more measurements instead.
On the 7th of October we had a very nice Kick-Off. I think we all got a good impression about the campaign and about the clouds we want to observe. We all got wet around noon when a convective cell overpassed the site. But it desappeared as fast as it appeared. So thanks to Tim for giving us the nice pictures (the big ones in the middle). He took both pictures within less then 2 hours difference. With those to pictures you already can get an impression about how variable the weather was on the 7th of October over Cabauw.
During this precipitation event one of the radars stopped working. This was fixed in the evening and it is now working continuously. But now one of our network connections is broken and we are working to fix that at the moment. The new equipment is bought and installed. And now waterproof!
We also measured some nice clouds that morning, so the first data are taken. We hope for more nice and cloudy days like that morning. Now the sun is shining and we hope for a nice sunset later
During the weekend we took the first measurements. For this all radar systems were pointing to the zenith that the measurements can be compared. The results of the comparrison will be the first data to look into. It will be a nice test to see different sensitivities of the instruments.
Today we put back the antenna elevation of TARA to 45 degree elevation and also put back the webcam. The pictures show that moving the antennas of TARA isn’t a fast process and even need some muscle power to make it work. Luckily also the weather turned into more cloudy conditions. So let’s hope , at least from our point of view, that it will become rainy and cloudy autumn. This would be nice for some nice measurements… Let’s see what the Kick-Off tomorrow will bring.
Last installation day. All the instruments are working fine at the moment so that first measurements for inter comparison are taken till Monday. So the antenna elevation of TARA was changed and but to the zenith. The other radar systems are set to the same elevation. Till the weather forecast looks that there will be a frontal overpass during the weekend the needed clouds will be there. Before the frontal overpass the conditions for cirrus clouds should be given. So it should be possible make some good measurements with the HALO camera system from LMU to. So on Monday we then know how stable the systems are working and how good the data look.
All the instruments are working fine, at least they collect some data if you plug in the electricity. So the second day was mainly to calibrate the instruments and to install the second Mira 35. Also some maintenance at TARA have been done.
Like the pictures show, calibrating the microwave radiometer involves handling liquid nitrogen. It is needed to create a low and stable temperature compared to the ambient one. This low temperature are needed to calibrate the sensors of the microwave radiometer. To test if the polarimetric capabilities of the Mira35-STAR mode radar are still correct some tests were made. A transmitter was installed to test if the receiver characteristics are still OK.
Also the quick-look page was part of the work from yesterday. As soon if all things work the link will appear in the weblog. Helium was also delivered. So now we can also launch some radiosondes. If you want to be in Cabauw during the first launch of the campaign register for the Kick Off on the 7th of October (see the post).
The containers with the instruments from TROPOS (Leibniz Institute for Tropospheric Research, Leipzig, Germany) were already waiting for us when we were arriving in the morning at Cabauw. So it was basically jumping out of the car and start to work. The LACROS container (Leipzig Aerosol and Clour Remote Observations System) was placed next to TARA. It is equipped with a cloud radar (Mira35, Metek), a microwave radiometer (RPG), a disdrometer, a ceilometer (JenOptic CHM 15k) and a Doppler lidar (HALO Photonics). A second container is placed next to the Cabauw tower. It contains a Raman lidar system (Polly).
After placing the containers the installation of the instruments begin. Screwing lags on instruments, fixing antenna for the radiosonde launches some first instrument tests have been made. So the laser beam of Polly is not hitting some cables at the tower and after changing the antenna of the radiosonde the noise in the radar was reduced significantly. In the evening also the second cloud radar arrived so that the whole setting can be tested today
Our colleagues from Munich were at the side. After inspection of several locations, and some discussions and phone calls they decided to go to the KNMI headquarter to set up their HALO camera.