Rosberg quickest at damp Barcelona

With the track not fully dry during the whole session, teams decided to limit their running, and only eight drivers took to the circuit during the day.

Rosberg and Williams teammate Kazuki Nakajima were basically the only ones to carry out proper running, covering 73 and 96 laps respectively, with the German finishing clearly ahead of his rivals with a best time of 1:30.675.

Mark Webber was third quickest in the Red Bull RB4, although the Australian covered just 26 laps. Teammate David Coulthard completed 22 on his way to the fifth fastest time.

The Red Bull duo were split by Fernando Alonso in the Renault, the Spaniard managing only 16 laps while his teammate Nelsinho Piquet covered eight.

"It was cold and wet today and so there was no point in doing a lot of running," Alonso said. "It was an opportunity to try the car in the wet, but it was so slippery that we did not do many laps.

"We waited in the afternoon for conditions to improve, but they did not so we ended the day slightly early."

Toyota's Jarno Trulli was the only other driver to complete some meaningful running with 57 laps. The team's test driver Kamui Kobayashi covered just an installation lap.

"Today was wet so it wasn't an ideal day for testing," said Trulli. "We were concentrating on testing some new parts for our new aerodynamics package. We made reasonable progress and collected some useful data but it's still too early to figure anything out yet.

"The track was changing throughout the day so direct comparisons were hard. In conditions like we had today we didn't do much mileage because we wanted to save some more miles and tyres for the next few days."

There were four red flags during the day, the first one caused by Piquet stopping just at the start of the session. He also caused the final one when he spun at Turn 5 before noon.

Two spins from Coulthard forced the session to be stopped again.

The McLaren team were scheduled to begin testing today, but the British squad decided against running due to the weather conditions. The team said they will review the conditions again tomorrow before deciding whether to run or not.

Today's times:

Pos  Driver        Team                      Time      Laps
 1.  Rosberg       Williams-Toyota      (B)  1:30.675   73
 2.  Nakajima      Williams-Toyota      (B)  1:32.370   96
 3.  Webber        Red Bull-Renault     (B)  1:32.599   26
 4.  Alonso        Renault              (B)  1:32.820   16
 5.  Coulthard     Red Bull-Renault     (B)  1:32.924   22
 6.  Trulli        Toyota               (B)  1:33.283   57
 7.  Piquet        Renault              (B)  1:40.073    8
 8.  Kobayashi     Toyota               (B)  no time     1

All Timing Unofficial