Ahead of today's second practice session, the air temperature is 33 degrees C, while the track temperature is 49 degrees C. It remains bright and sunny.

That said, at present it is claimed that it is 100percent certain that Sunday's race will be wet, which would invalidate everything the drivers are doing today, though it would make pole position more important than ever.

Lewis Hamilton topped the timesheets this morning, ahead of Sebastian Vettel, Mark Webber and Jenson Button, the four covered by just 0.086s. However, with all twenty-four drivers using a mixture of 2012 and 2013-spec tyres it was difficult to make a comparison.

World championship hopeful Fernando Alonso was fifth quickest, a late charge on 2013-spec tyres seeing him close to within 0.261s of Hamilton who was clearly frustrated at his team's insistence at spending so much time on the newer rubber.

Mercedes was disappointing this morning, particularly Nico Rosberg, while both Sauber drivers encountered brake problems.

Problems for Kimi Raikkonen also, the Finn losing time while his team worked on his engine, at one stage changing the spark plugs.

Bruno Senna and Heikki Kovalainen sat out this morning's session, both handing over their cars to their teams third drivers. Ironically, neither driver has secured a berth for next season yet.

Grosjean heads down the pitlane as the lights turn green, the Frenchman followed by Ricciardo and Maldonado.

As Ricciardo posts a 17.648 there are already seventeen drivers on track including most of the big guns. All are on the harder rubber.

Raikkonen goes quickest (16.538) and Button second (16.629), only to be demoted when Grosjean improves with a 16.070.

Webber posts (16.000) having gone quickest in S3, however, moments later Hamilton bangs in a 15.893.

Vettel and Alonso side-by-side heading on the long climb up to the start/finish straight. The German is on a flying lap, the Spaniard on his out lap.

The times tumble, Rosberg, Alonso, Webber and Massa all going quicker, the Brazilian crossing the line at 15.473.

A big lock-up for di Resta, caught beautifully by the slo-mo cameras. Elsewhere, Hulkenberg asks "what happened to the rears?" the 2013 rubber continuing to show a tendency to overheat.

No sooner has Alonso raised the bar with a 15.274 than Vettel raises it just that little bit higher, the German crossing the line at 15.226. No sign of the HRT duo yet, indeed, there are very few people in the Spanish outfit's garage.

Button splits the title contenders with a 15.256, the Englishman looking good today, mindful of the fact that he is effectively team leader next season.

A massive lock-up for Raikkonen at T1, the Finn subsequently running over the massive run-off.

After twenty-five minutes, Vergne and Pic are the first to switch to the medium (option) rubber.

Webber improves to fourth (15.336) having gone quickest in S2. The top seven - Vettel, Button, Alonso, Webber, Hamilton, Massa and Schumacher - are covered by just 0.251s.

Massa, having previously taken a very bumpy ride over the kerbs, now does a Raikkonen by locking-up heavily at T1.

As the cameras pick out Martin Whitmarsh and Ross Brawn having a quiet chat, Alonso goes quickest with a 15.150.

At 50:00, the HRT duo are finally on track, the team claiming that its non-appearance up to now was due to it wanting the temperature to fall. Yeh right!

A 15.182 sees Grosjean split Alonso and Vettel at the top of the timesheets, the Frenchman having switched to the option rubber. Next time around he improves to 14.994 to go quickest.

Raikkonen and Kobayashi are the next to switch to the softer rubber, the Finn immediately improving to sixth (15.371).

At half-time, it's: Grosjean, Alonso, Vettel, Button, Webber, Raikkonen, Rosberg, Hamilton, Massa and Schumacher. The ten are covered by 0.483s.