Hi Jingyi- What was the date and location for the photograph? This information often helps in ID. This is a Marbled Godwit. Note the really long, slightly upturned bill, overall buff and orange-buff coloration and scaly back.
Jingyi, you'll get 3 big brown shorebirds out there in CA. The first thing to note is that the Marbled Godwit's bill turns up but the other two turn down. If it's a turned down bill, it will either be a Long-billed Curlew or a Whimbrel (formerly Hudsonian Curlew, so it's a curlew too). If you have a curlew, look at the length of the bill and the head pattern. Long-billed has a longer bill (what a shock!) and a plainish head and the Whimbrel has a shorter bill and a striped head.
All of these birds are dynamic and extremely photogenic, but I don't think they say that in any of the field guides.
As stated by others, this is indeed a Marbled Godwit. I think that it is even possible to sex this bird. The bill looks fairly long and the upturn is barely perceptible, which would indicate that it is a female. Male godwits have comparatively shorter bills and their bills are slightly more upturned. If you go to the link below and look at images #3 (female) and #6 (male) you can see how much difference there is in the length and curvature of Marbled Godwit bills.